BajaNomad - About Differentials and Traction Control

About Differentials and Traction Control

Pages: 1 2

David K - 12-28-2010 at 09:47 AM

Inspired by a Nomad's u2u, here is a brief explanation of 2WD vs. 4WD and Open Differentials vs. Limited Slip Differentials, Locked Differentials, Traction Control and A-TRAC.

Differentials: Transfer torque (engine power) from the driveshaft to both tires on that axle equally UNTIL one tire needs to rotate more than the other... This happens when turning, and is the reason for a differential (to allow the outside tire to rotate more than the inside). Otherwise, there would be binding and scuffing on hard surfaces. These are normal 'open differentials'.

The negative part of an open differential when off roading is that the tire that rotates the easiest gets the engine torque and spins. The tire that has traction on firm ground does nothing. A 2WD gets stuck the easiest because of this... only one of the 4 tires will spin. The movie 'My Cousin Vinny' does a great job explaining this.

4WD has front and rear differentials so you double the possibility of moving through difficult terrain... Usually that is enough, but not always as 4WDs get stuck too, but is worse places!

If one front tire and one rear tire have no traction (on ice, mud, etc.), you will be stuck, as torque goes automatically to those two, low traction tires. You will notice that only one front and one rear tire will spin when stuck. Lowering the tires' air pressure is one way to increase traction. This is how we cross deep, loose sand.

LIMITED SLIP differentials have clutches or other mechanisms inside them that will brake the faster spinning side so more torque will be shared with the opposite tire. Posi-traction is one brand of limited slip differentials.

TRACTION CONTROL is newer technology that uses rotation sensors on each tire, and the car's brakes, to slow down a free spinning tire. This action will transfer torque to the traction tire. In 4WD, this is a big help in soft terrain or hill climbing.

LOCKING DIFFERENTIALs are now standard on many 4WD vehicles, most often on the rear differential only. Sometimes on the front, too as on Jeep Rubicons. When you 'lock' the differential, a gear goes into place that connects both sides of the differential (both tires) together. This divides torque 50-50. The loose tire rotates no more than the traction tire... you will move ahead with just one of these tires on firm ground.

The negative part of lockers is that steering is very difficult on hard ground, so lockers are recommended to be used only for emergency conditions and only at slow speed.

A-TRAC (Active Traction Control) is available on some Toyota and Lexus models (and under different names by some other companies perhaps). A-TRAC is big step up from basic TRACTION CONTROL in that the braking of a non-traction tire is much firmer and basically locks its rotation to the opposite traction tire. A-TRAC provides the traction of front and rear lockers, but without the steering issues. No speed or safety concerns with A-TRAC. It does only work in LOW RANGE, however. The A-TRAC does make noise, but works!

In the Off Road TRD 4WD Tacoma of 2009+ there is TRAC (traction control) in 2WD and 4WD High, and A-TRAC in 4WD Low.

sanquintinsince73 - 12-28-2010 at 09:57 AM

Great information, DK. So basically when I switch to 4x4 on my suburban only 1 front and 1 rear are spinning. Years ago I had a Toyota where I had to get out and manually lock the front hubs. That vehicle handled off-road situations a heck of alot better than anything I've used since. With my suburban I do alot of sand dunes in San Quintin and it handles just ok.

AWD

baron - 12-28-2010 at 10:10 AM

Good info
Now can someone explain how my 2007 GMC Savana AWD van drive train works? Muchas gracias

Sherman - 12-28-2010 at 10:46 AM

Quote:

Originally posted by sanquintinsince73
Great information, DK. So basically when I switch to 4x4 on my suburban only 1 front and 1 rear are spinning. Years ago I had a Toyota where I had to get out and manually lock the front hubs. That vehicle handled off-road situations a heck of alot better than anything I've used since. With my suburban I do alot of sand dunes in San Quintin and it handles just ok.

My understanding of locking hubs is that they free the front axle and differential from being driven by the forward motion of the vehicle's front wheels when the transfer case is in 2WD mode. This saves wear & tear on the front drive shaft, universal joints and bearings, and gives a slight increase in MPG. If I recall from owners manuals from the Travel-All's, Jeeps, and Toyota's I've owned, it was recommended to engage the hubs from time to time to ensure lubrication of those parts that would stay idle if in 2WD mode with hubs disengaged. Once engaged, the front drive on these would perform as described above, if not limited slip, only one wheel would spin in a stuck situation. Putting the trans in reverse, would reverse the wheel that spins, thus the trick of "rocking" a vehicle to un-stick it, by quickly shifting back and forth from forward to reverse.

[Edited on 12-28-2010 by Sherman]

TMW - 12-28-2010 at 10:57 AM

Quote:

Not necessarily. Most GM trucks and large SUVs come with a locking differental in the rear that was locked below 25mph and unlocked above. You can test by raising one side in the rear and try to turn the wheel.

[Edited on 12-28-2010 by TW]

TMW - 12-28-2010 at 11:08 AM

Sherman manually locking hubs disconecct the wheel from the drive axle at the wheel. Self locking front hubs are disconected in the differential and the transfer case disconnects the drive to the front differential in both cases.

David K - 12-28-2010 at 12:47 PM

Quote:

Originally posted by baron
Good info
Now can someone explain how my 2007 GMC Savana AWD van drive train works? Muchas gracias

AWD 'All Wheel Drive' (Full Time 4WD) has a third or center differential that allows the front and rear driveshaft to turn at different speeds (when turning). 4WD (Part Time 4WD) vehicles when in 4WD have the front and rear driveshafts locked and should NOT be driven on dry pavement as any turning will cause a bind between the two driveshafts.

Some AWDs have a center differential lockout for true 4WD when off roading. Otherwise the split in torque is not even between the front and rear in AWD.

David K - 12-28-2010 at 12:53 PM

Quote:

Originally posted by TW
Sherman manually locking hubs disconecct the wheel from the drive axle at the wheel. Self locking front hubs are disconected in the differential and the transfer case disconnects the drive to the front differential in both cases.

Originally, there were 'self locking hubs'... my dad had them on the Wagoneer... The only issues was to go back into 2WD and unlock the hubs, you needed to drive in reverse a bit.

Today, to free up the front drive components, an 'ADD' is used instead of hubs. ADD is Automatic Disconnecting Differential... my Tacoma has this... and allows shift-on-the-fly engaging of 4WD up to 55 mph and disengaging, too... No backing up required. A 'fork' is applied to one side of the differential for 4WD, and when it is retracted, as when an open differential has no traction on one side, neither side gets any torque.

David K - 12-28-2010 at 01:05 PM

Quote:

Well... if one side of the vehicle is on firmer ground than the other... then the tries on the loose soil side will spin.

In soft sand or mud, etc. where all the surface is loose and you no longer have forward movement (too much air in the tires, perhaps)... You may see one rear and one front tire spinning... The other two are getting torque, just not enough to rotate. It makes it seem that 4WD is really just 2WD (one front and one back working) and 2WD is just 1WD.

Either tire will get torque, depends which one has more traction... torque goes to the tire with LESS traction with standard/ open differentials. This is great when turning on dry roads... but terrible when trying to go through bad terrain or up steep hills with loose rocks.

New cars and trucks are getting tracion control and VSC (Vehicle Stability Control) along with it. VSC used on my truck was invented by Bosch.

VSC has been said to be the greatest safety feature to come to automobiles since the seat belt!

VSC automatically straightens your vehicle out if it begins to go into a spin on the highway should you make a sudden sweve to avoid hitting something.

Every Toyota now has TRAC and VSC... as well as many other car companies.

bigboy - 12-28-2010 at 06:27 PM

David, return to engineering school as soon as possible! Open diffs always have equal torque applied to both wheels. The wheel that is spinning on mud or ice has the same amount of torque as the wheel that is on firm ground. Just imagine a one wheel drive vehicle. When power is applied to one wheel only, the car would rotate around that drive wheel. A better way to picture this is to think what would happen if you only had braking on one wheel. Upon breaking even moderately, the car would spin or severely pull every time the brakes are applied.

David K - 12-28-2010 at 06:33 PM

big boy... I didn't go to 'engineering school', I tried to write it in non-mechanical terms... if I used "torque" incorrectly, then what is the correct word for the rotation energy from the engine that is diverted to the low traction tire from the differential?

bigboy - 12-28-2010 at 09:32 PM

David.....open difs will work as well as any differential as long as the traction is the same for both wheels or in the case of four wheel drive, all wheels. In a 4X4 situation in sand on level ground, open differentials will work as well as the other difs mentioned. All four wheels will be driven and no slippage will be incurred if both wheels, per axle, have the same weight and surface conditions. Where they don't work as well is off road situations where one wheel, on that axle, is in the air or on a slippery surface and the other wheel is on a hard surface with more traction.

In the case where one wheel is in the air, the power delivered to both wheels on that axle will be nothing since the torque will be equal on a open differential. This is where the other kinds of differentials shine that you mentioned in your post.

David K - 12-28-2010 at 10:23 PM

Quote:

Originally posted by bigboy
David.....open difs will work as well as any differential as long as the traction is the same for both wheels or in the case of four wheel drive, all wheels. In a 4X4 situation in sand on level ground, open differentials will work as well as the other difs mentioned. All four wheels will be driven and no slippage will be incurred if both wheels, per axle, have the same weight and surface conditions. Where they don't work as well is off road situations where one wheel, on that axle, is in the air or on a slippery surface and the other wheel is on a hard surface with more traction.

In the case where one wheel is in the air, the power delivered to both wheels on that axle will be nothing since the torque will be equal on a open differential. This is where the other kinds of differentials shine that you mentioned in your post.

Yes, that's the point about limited slip transfering 'torque' or instead of a spinning tire in the air, you get a tire pushing against the ground to move you ahead. You rarely have equal traction conditions under all four tires at the same time when you are off the highway. Even when the surface is the same... torque/ power/ whatever you want to call it is biased to just one tire per axle.

In sand, if I bog down (from too much air in the tires)... even though the surface condition is equal... you still will have one front and one opposite side rear tire spinning more than the other on each axle. This may be due to the vehicle weight distribution, but is the case with open differentials.

I discovered last January that Traction Control (automatic limited slip) allowed me to wheel all over the beach at Bahia Santa Maria without deflating... which was a first after years and years of four wheeling there.

To test it and see if it wasn't just some kind of fluke... I de-activated the traction control and had only open differentials in 4WD High... and the truck bogged down and got stuck...

Without letting any air out or clearing away the sand from the tires... I turned on the A-TRAC (in 4WD Low) and the truck climbed out of the stuck! I went back into High Range with standard TRAC back on, and drove about again, with ease!

I was totally blown away by the new Toyota system and have continued 'testing' it ever since!

In the summer, with a heavy load, I did need to lower the tire pressure so as to not dig in so much... Temperature does affect sand driving. However, on many other occaisions the limited slip of TRAC and the 'automatic lockers' of A-TRAC have shown me what a big step forward technology has made in traction ability.

from Wikipedia

David K - 12-29-2010 at 10:58 AM

>>>So far, the word torque seems correct... (I still would like to be corrected if there is a better word to describe the power that turns a wheel on a vehicle)<<<

Torque, also called moment or moment of force (see the terminology below), is the tendency of a force to rotate an object about an axis,[1] fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

Understanding the relationship between torque, power and engine speed is vital in automotive engineering, concerned as it is with transmitting power from the engine through the drive train to the wheels.
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Differential:

A vehicle's wheels rotate at different speeds, mainly when turning corners. The differential is designed to drive a pair of wheels with equal torque while allowing them to rotate at different speeds.

In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism.

When cornering, the inner wheel needs to travel a shorter distance than the outer wheel, so with no differential, the result is the inner wheel spinning and/or the outer wheel dragging, and this results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the entire drivetrain.

Input torque is applied to the ring gear (blue), which turns the entire carrier (blue). The carrier is connected to both the side gears (red and yellow) only through the planet gear (green) (visual appearances in the diagram notwithstanding). Torque is transmitted to the side gears through the planet gear. The planet gear revolves around the axis of the carrier, driving the side gears. If the resistance at both wheels is equal, the planet gear revolves without spinning about its own axis, and both wheels turn at the same rate.

If the left side gear (red) encounters resistance, the planet gear (green) spins as well as revolving, allowing the left side gear to slow down, with an equal speeding up of the right side gear (yellow).

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Loss of Traction:

The torque applied to each driving wheel is a result of the engine, transmission and drive axles applying a twisting force against the resistance of the traction at that roadwheel.

Unless the load is exceptionally high, the drivetrain can usually supply as much torque as necessary, so the limiting factor is usually the traction under each wheel. It is therefore convenient to define traction as the amount of torque that can be generated between the tire and the road surface, before the wheel starts to slip.

If the torque applied to drive wheels does not exceed the threshold of traction, the vehicle will be propelled in the desired direction; if not, then one or more wheels will simply spin.

To illustrate how a conventional "open" (non-locked or otherwise traction-aided) differential can limit torque applied to the driving wheels, imagine a simple rear-wheel drive vehicle, with one rear roadwheel on asphalt with good grip, and the other on a patch of slippery ice. With the load, gradient, etc. The vehicle requires a certain amount of torque applied to the drive wheels to move forward. If the two roadwheels were driven without a differential, each roadwheel would be supplied with an equal amount of torque, and would push against the road surface as hard as possible. The roadwheel on ice would quickly reach the limit of traction, but would be unable to spin because the other roadwheel has good traction. The traction of the asphalt plus the small extra traction from the ice exceeds the minimum requirement, so the vehicle will be propelled forward.

*** With an open differential, however, as soon as the "ice wheel" exceeds the threshold of traction available (which varies depending on tire size, type, and inflation pressure, vehicle weight and proportioning, temperature, etc.), it will start to spin, further reducing traction (the amount of torque required to spin the wheel against traction lowers after the threshold is initially broken).

Since an open differential limits total torque applied both drive wheels as the amount utilized by the lower traction wheel multiplied by a factor of 2, when one wheel is on a slippery surface, the total torque applied to the driving wheels will be lower than the minimum torque required for vehicle propulsion. thus, the vehicle will not be propelled. :light:

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Many newer vehicles feature traction control, which partially mitigates the poor traction characteristics of an open differential by using the anti-lock braking system to limit or stop the slippage of the low traction wheel, thus transferring more torque to the wheel with good traction. While not as effective in propelling a vehicle under poor traction conditions as a traction-aided differential, it is better than a simple mechanical open differential with no electronic traction assistance.

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There are various devices for getting more usable traction from vehicles with differentials.

One solution is the Positive Traction (Posi), the most well-known of which is the clutch-type. With this differential, the side gears are coupled to the carrier via a multi-disc clutch which allows extra torque to be sent to the wheel with higher resistance then available at the other driven roadwheel when the limit of friction is reached at that other wheel. Below the limit of friction more torque goes to the slower (inside) wheel.

A limited slip differential (LSD) or anti-spin is another type of traction aiding device that uses a mechanical system that activates under centrifugul force to positively lock the left and right spider gears together when one wheel spins a certain amount faster than the other. This type behaves as an open differential unless one wheel begins to spin and exceeds that threshold.

While positraction units can be of varying strength, some of them with high enough friction to cause an inside tire to spin or outside tire to drag in turns like a spooled differential, the LSD will remain open unless enough torque is applied to cause one wheel to loose traction and spin, at which point it will engage.

A LSD can use clutches like a posi when engaged, or may also be a solid mechanical connection like a locker or spool. It is called limited slip because it does just that; it limits the amount that one wheel can "slip" (spin).

A locking differential, such as ones using differential gears in normal use but using air or electrically controlled mechanical system, which when locked allow no difference in speed between the two wheels on the axle. They employ a mechanism for allowing the axles to be locked relative to each other, causing both wheels to turn at the same speed regardless of which has more traction; this is equivalent to effectively bypassing the differential gears entirely.

Other locking systems may not even use differential gears but instead drive one wheel or both depending on torque value and direction. Automatic mechanical lockers do allow for some differntiation under certain load conditions, while a selectable locker typically couples both axles with a solid mechanical connection like a spool when engaged.

Electronic traction control systems usually use the anti-lock braking system (ABS) roadwheel speed sensors to detect a spinning roadwheel, and apply the brake to that wheel. This progressively raises the reaction torque at that roadwheel, and the differential compensates by transmitting more torque through the other roadwheel—the one with better traction.

:light:

DENNIS - 12-29-2010 at 11:06 AM

Quote:

Originally posted by bigboy
David, return to engineering school as soon as possible!

What a nice, civilized way to say something else. :lol:

TMW - 12-29-2010 at 11:08 AM

According to my copy of Manual Transmissions and Transaxles 4th addition by Jack Erjavec page 177 it says When a car is stuck in mud or snow, one drive wheel spins while the other remains stationary. In this example, the differential is transferring all of the torque and rotary motion to the drive wheel with the least resistance. Resistance, in this case, means traction. Applying torque to the wheel without traction does little good while trying to move the car

David K - 12-29-2010 at 11:11 AM

Quote:

Originally posted by TW
According to my copy of Manual Transmissions and Transaxles 4th addition by Jack Erjavec page 177 it says When a car is stuck in mud or snow, one drive wheel spins while the other remains stationary. In this example, the differential is transferring all of the torque and rotary motion to the drive wheel with the least resistance. Resistance, in this case, means traction. Applying torque to the wheel without traction does little good while trying to move the car

BINGO!

(thanks for that TW... it is what I have been saying... and I didn't need to go back to engineering school :rolleyes:

)

4x4abc - 1-18-2011 at 07:53 PM

David,

I admire your work! You know so much more about Baja than I - but I know differentials better.
4x4 has been my field for 25 years.
You are a little off about what's happening with torque in a wheel spin situation.
Even though the web and books are full of "all torque goes to the slipping wheel" - physics books tell a different story.

And when you checked wikipedia it was right in front of your eyes: "A vehicle's wheels rotate at different speeds, mainly when turning corners. The differential is designed to drive a pair of wheels with equal torque while allowing them to rotate at different speeds"

So, the open (no lockers, no limited slip) differential always sends equal torque to both wheels. Always!
Always, as in a straight line, in turns, with a wheel on slippery surface - even with one wheel in the air.

The wiki article has a decent description of what's happening when the two connected wheels encounter unequal traction. Let me paraphrase it: A vehicle needs a certain amount of torque to me moved. On high traction surfaces it will be almost impossible to get a tire to slip and spin - the amount of torque generated on both tires is very high = the vehicle can accelerate quickly.
If the driven axle would encounter a mixed surface (asphalt/sand) the tire on sand might slip and spin. However, the amount of torque to get a tire to spin on sand requires a certain amount of torque (called threshold - see wiki above). Since the rule is that an open differential always distributes torque equally - the tire with more traction will get the same amount as the slipping tire. Threshold times two. And in this case the vehicle might still be moving, because twice the amount of low torque might be sufficient to move the car. Depends.
A slipping and spinning tire by itself is not an indicator that the car will not move. Think of high HP cars laying rubber with slipping and spinning tires - they do indeed move.

Here is where Baja and off-road comes in. Sometimes one tire has so little traction that the threshold torque generated is so low that even doubling it (remember, the other tire gets the same amount) will not be sufficient to move the truck. 2 times a very low amount is still a very low amount.
But drive system might be just missing an additional 20 lb-ft. So your friend's strong shoulder (threshold torque times two plus friend's torque) is enough to move the car.

Now, the description so far was only for a one axle 2WD - but most of have 4WD, so we are safe, right? Not necessarily.
Almost always (the "why" would be too lengthy in one post) if one tire slips and spins the diagonally opposed wheel on the other axle will also slip and spin. Those two diagonally opposed wheels will slip and spin later than the one wheel on a 2WD. Because each tire of a 4WD will have to generate only half the amount of torque as the wheels on a 2WD (given that both cars are of equal weight)
But since we usually drive where no 2WD dares to go, we get stuck due to low threshold torque.

Don't feel to badly about not knowing exactly how the differential does its work. Even the wiki contributors goof on occasion. In the 'Loss of traction' section above you copied from their site: " If the two roadwheels were driven without a differential, each roadwheel would be supplied with an equal amount of torque, and would push against the road surface as hard as possible."
That is dead wrong.
When no differential is present, the tire with more traction will generate the most torque - the one with less traction will generate less. So there will be higher mechanical stress on the axle shaft going to the wheel with more traction.
Rule for axles with differential locks engaged (equal to not having a differential) is: Wheel rotations are equal - torque is unequal.
To repeat open differential: Wheel rotations are unequal - torque is equal.

more: http://www.4x4abc.com/4WD101/

I'll be happy to outline some of the measures that can be taken if one does not have limited slip, traction control or selectable lockers.

David K - 1-19-2011 at 12:05 AM

Thank you Harald... so what is the best way to describe the effect of slowing the spinning tire down so the traction tire can move the vehicle (as with limited slip).

I can picture the process... but using 'torque' was technically wrong, yet most understand what is happening...

Both tires get 'torque' when one is spinning freely in the air or on ice... But the tire on firm ground does nothing to move the vehicle until the spinning tire is braked (limited slip or locker) to slow it down or match its rotation with the other tire.

Until the spinner is slowed or stopped, the energy is lost to it... When it is slowed or stopped the 'energy' (what I called torque) then goes to turn the tire on fiorm ground.

What is the correct term I need to answer this in simple to understand terms?

Muchas Gracias!

4x4abc - 1-19-2011 at 08:05 AM

David,

you were absolutely correct when you used 'torque' - you were only off by saying torque only goes to the spinning wheel.

Follow me on this little excursion:

rules first
The traction each tire has on the ground is the counterforce for torque - without a counterforce (traction or resistance) no torque can be created.
In order to avoid spinning tires, you have to have an equal or higher amount of traction than the amount of torque applied.
An open differential always distributes torque equally while allowing both wheels to rotate at a proportional different rate (if one goes 10 rpm faster, the other one will slow down 10 rpm - if one stops, the other will rotate twice as fast as before).

Just for arguments sake, lets say a car needs 100 units of torque to start moving.
At the beginning of our experiment the car is on high traction asphalt. 100 units of traction under each wheel. So when I step on the gas, increasing the torque, the car will start moving when each tire generates at least 50 units of torque (50 + 50). I still have 50 units of traction on each wheel to spare (we need some of it for lateral stability).

New test. One wheel on dry asphalt, one wheel on sand. Sand has about 40% of the traction dry asphalt has. So, 100 units of traction at the wheel on asphalt - 40 units of traction at the wheel on sand. When I step on the gas and reach the threshold torque of 40 units at the wheel on sand, that tire will start slipping. Since the rule is, that the open diff apportions torque equally, the wheel on asphalt also get 40 units of torque. 40 + 40 = 80
80 units of torque is not enough to move the car - we need 100.
Someone willing to push the car would easily be able to generate additional 20 units of torque and get the car moving.

Here is what traction control would do. The computer would send a signal to apply the brake (pulsating like ABS) at the wheel that is starting to slip. The brake will have to create additional 20 units of resistance. 20 + 40 is 60 at the wheel on sand - so the other wheel will also get 60, together that's 120 (20 of the will turn into heat due to the brake friction) and the car starts moving.
The advantage is that traction control always only adds as much resistance (friction) as needed at the wheel(s) that slip. Disadvantage is that the system is reactive. You have to get the wheel(s) slipping first before traction control steps in to save your tush.

Limited slip. By installing clutch plates inside the differential the internal parts are much harder to move. They put up resistance. This amount of "preload" is fixed when first installed. So, lets say, each axle half puts up a resistance of 30 units, then your wheel on sand would not even slip because I have a total counter force of 40 + 30 at that wheel. 70 at the other wheel. 140 in total - of which 110 are usable (30 turn into heat).
So, advantage is that this system is proactive - it keeps the wheels from slipping in the first place. Disadvantage is that the threshold is fixed and might not be sufficient for really slippery stuff. Also, clutch plates wear out and the effectiveness of limited slip is going away over time.

There are some other limited slip concepts I will not go into to keep things easy. They have all one thing in common - they limit slip, but they do not prevent it entirely.

Another test. One wheel on dry asphalt, one wheel on ice. Ice has about 10% of the traction dry asphalt has. So, 100 units of traction at the wheel on asphalt - 10 units of traction at the wheel on ice. Will my limited slip (30 preload) save me?
Lets see - 10 + 30 = 40 at the wheel on ice - 40 as well at the high traction wheel. Meaning I can't generate enough torque to get moving. The wheel on ice will slip.
This shows you that limited slip is an acceptable assistant for some conditions, but not for all.

were you able to follow?

this might help to illustrate:
http://www.youtube.com/watch?v=iAlro4aKPWM&feature=playe...

[Edited on 1-19-2011 by 4x4abc]

[Edited on 1-19-2011 by 4x4abc]

bigboy - 1-19-2011 at 09:55 AM

Thank you 4X4abc for you excellent response. Just about everyone I know has it wrong about open differentials. I've had many discussions with 4X4 friends that think like David about open differentials.
I do have an engineering background but I get tired of trying to explain the workings of the different types of drive axles.

David K - 1-19-2011 at 10:18 AM

Thanks very much Harald!

I was trying to use fewer words at getting the idea across of how limited slip, traction control, and lockers will give you more ability off road than without (open differentials).

Seems that torque is both energy 'at rest' when matched with friction of road surface, and energy in motion when rotating the tire. My error was saying it was just the force used to rotate the tire.

Your answer helps to understand how just a push from a friend in back when you get stuck is often enough to move your 3,000 pound car.

4x4abc - 1-19-2011 at 11:26 AM

David,

thank you for thanking me - teachers so rarely get some positive feedback.
I have been screamed at in other forum trying to help them out. "Don't try and confuse me with facts!" was probably the most irritating response.

But I also know how hard it is to let go of "We have always done it this way."

David K - 1-19-2011 at 11:44 AM

Quote:

Originally posted by 4x4abc
David,

thank you for thanking me - teachers so rarely get some positive feedback.
I have been screamed at in other forum trying to help them out. "Don't try and confuse me with facts!" was probably the most irritating response.

But I also know how hard it is to let go of "We have always done it this way."

Oh no, I appreciate facts and being corrected... I want only to pass along the truth... I was just trying to make it easy to understand.

Please keep posting good stuff... The history of Baja as well as the four wheel drive adventures there are just GREAT subjects... The Nomads are tired of me bringing them up, so new blood here is good!

You would like to meet up with BajaTripper (Steve) who lives in La Paz, perhaps? Steve was with us on the Santa Maria trip. His mother (BajaLera) is writing a book on the early native inhabitants of Baja...

I am going to post on the Cochimi language I am reading about, as well...

meeting

4x4abc - 1-19-2011 at 12:10 PM

sure, any time

BajaGringo - 1-19-2011 at 01:36 PM

Thanks for the lesson on differentials guys. And I thought I had them all figured out before reading this thread...

:lol:

Baja12valve - 1-19-2011 at 06:39 PM

One more item concerning the clutch type LSD's. You can arrange them to increase the torque transfer or bias ratio. Looking at the U-tube video it was interesting to see the Dodge spin both wheels on the rollers, transferring little torque to the traction wheels and as a result, it got stuck pulling the boat. That is probably a factory setting of the clutches. Just because you have a LSD, it does not mean that you have a good transfer of torque from one wheel to the other. I have arranged both front and rear to be aggressive. If I lift 3 wheels in the air and put the axles on large, strong pads, not blocks, my remaining front wheel will burn rubber, pulling the truck off the pads. The other front wheel in the air is not spinning at all. A locker spin move both.
For those with the Toyota A-TRAC, I would be willing to drop chains, go bumper to bumper and gladly pull you around the parking lot, LOL.

David K - 1-19-2011 at 06:57 PM

Now, now... the A-TRAC will pull its own weight even if only one tire (even a front tire) is the only one with traction.

While not the same as front lockers, and stronger than normal limited slip, it comes on my truck as standard equipment with the Off Road package... and the A-TRAC doesn't interfere with steering ability that lockers do.

Baja12valve - 1-19-2011 at 09:29 PM

No worries :biggrin:

I was hoping you would bite the hook

David K - 1-19-2011 at 10:40 PM

What were you thinking!? Of course I would! :rolleyes:

David K - 3-30-2012 at 03:34 PM

A revisit of a good thread!

4x4abc - 3-30-2012 at 04:07 PM

good David!
I was about to come back to this issue anyway - this time with a little different angle. So, stay tuned.

David K - 3-30-2012 at 04:09 PM

That will be great Harald!!! :light:

Not brake-controlled, 100% Locked

Ken Cooke - 3-30-2012 at 05:57 PM

Not center-locked, not brake-controlled, but air-locked - 100% Traction to each tire.

Here is my Jeep in Baja doing what Rubicons are known for doing - rock-crawling. (Enough said) :yes:

Explaining Limited Slip Differentials

David K - 3-30-2012 at 06:00 PM

Nobody does it better than Miss Mona Lisa Vito, on 'My Cousin Vinny' (between minute 1:30 and 3:45 in this clip) (also explains independent suspension vs. solid axle) :lol:

Rubicon Owners of CA in Johnson Valley, CA

Ken Cooke - 3-30-2012 at 07:41 PM

This will show what both Air-Locked ('03-'06) and Electric-Locked ('07+) vehicles are capable of when using their traction-devices. I am curious what an A-TRAC vehicle could do in this terrain. An FJ Cruiser was parked near the trail, but not running the actual trail due to its rough nature. Enjoy!

DAVID K and diffs

captkw - 3-30-2012 at 08:12 PM

HOLA all,david you,,, all always, correct..being this is part of my job..I stayed on the side line's and did not open my Big mouth !! now I throw a little bit in..their is also what is known as air lockers and they work rather well and for baja ... locking the spider = full pozie....you will also have a great air compresser on board for airing up !! K&T... :cool:

PS..the company is ARB

[Edited on 3-31-2012 by captkw]

[Edited on 3-31-2012 by captkw]

David K - 3-30-2012 at 09:34 PM

Yup, for enough thousand dollar bills, anyone can have ARB lockers front and back... so far, the Toyota A-TRAC system has taken me everywhere I wanted to go with ease... and I paid nothing extra for it on my Tacoma. But, thanks... On the Mision Santa Maria trip the vehicles with ARB lockers did no better (or worse) than my A-TRAC... one thing that Art pointed out... A-TRAC did not need to be turned off to make the sharp turns. :light:

Fernweh - 3-31-2012 at 10:49 AM

Part of this whole equation, regardless of all the fine vehicles with their nice equipment, is definitely the skill level of the driver.

As Harald had mentioned before all the fancy electronic ESP, A-track and other computerized "4x4" systems - are reactive ones. The traction control system has to first encounter some adverse conditions, before it will react.

The driver controlled differential locks are proactive traction devices. The (hopefully) skilled driver has to read the trail and he has to make the decision when to use the diff locks and which ones - before the vehicle gets into "trouble".

Karl

[Edited on 3-31-2012 by Fernweh]

Detroit front/arb rear

classicbajabronco - 3-31-2012 at 11:13 AM

I'm running an ARB in the front and a detroit in the rear of my 66 bronco. wish I would have done the reverse though and ran the detroit in the front and the ARB out back.

The detroit in the rear makes a lot of noise and pops/clicks and tires the chirp on pavement. In the front it doesn't matter once the hubs are unlocked or the front axle is disengaged via the twin stick transfer case. An ARB in the front is a waste of money, unless you really want airlockers. they are awesome out back, as it gives you 100% lockup offroad and 100% open for on-road manners.

The eb never sees pavement though... so it is not an issue.

David K - 3-31-2012 at 11:38 AM

Quote:

Originally posted by Fernweh
Part of this whole equation, regardless of all the fine vehicles with their nice equipment, is definitely the skill level of the driver.

As Harald had mentioned before all the fancy electronic ESP, A-track and other computerized "4x4" systems - are reactive ones. The traction control system has to first encounter some adverse conditions, before it will react.

The driver controlled differential locks are proactive traction devices. The (hopefully) skilled driver has to read the trail and he has to make the decision when to use the diff locks and which ones - before the vehicle gets into "trouble".

Karl

[Edited on 3-31-2012 by Fernweh]

Agree... and the best way to descibe A-TRAC is it is like having 'automatic lockers on all 4 tires. You have open differentials, so steering is never a problem or chirping on hard ground (granite or asphalt), but as soon as any tire(s) loose traction, the A-TRAC goes to work and applies the amount of brake force to the spinning tire to match it with the traction tire... then they both rotate at the same rate as you move forward.

So, it is far superior to limited slip differentials or standard traction controls which in both cases have a limited amount of force and thus can only slow down the spin speed of the loose tire and not match it with the traction tire... which may not be enough to move you ahead.

A-TRAC is not as 100% as front and rear lockers, because (as you said) it is a reactive system and doesn't go to work until you need it... so some spin will happen first. Lockers keep you crawling ahead without any brief spin of any tire.

The Tacoma Off Road 4WD does also have a rear locker, and you can have it and A-TRAC on at the same time... so if your forward speed ever comes to a stop or nearly a stop (under 3 mph), the A-TRAC reacts on the front tires to find traction.

[Edited on 4-15-2012 by David K]

Fernweh - 3-31-2012 at 11:51 AM

DavidK,

we should ask Harald (4x4abc) what he would call a true full time, all-wheel 4x4 drive truck which has both traction control systems.
The computerized ESP and the mechanical differential lockers, not only on the front and rear axle, but also a diff locker in the center - the transfer case.

Would be interesting to hear his view on it :yes:

David K - 3-31-2012 at 12:09 PM

I would bet he would agree that manual hubs beat an ADD (or auto. locking hubs), and lockers beat any traction control system.

So far, and after three Tacomas with an ADD (automatic disconnecting differential), no problems with the shift-on-the-fly 4WD.

All 3 of my Tacomas had the rear locker, and while it sometimes takes a couple of tries to lock it, they all have worked. My current Tacoma with all the electronic traction controls has actually been the best off roader of them all, and I attribute that to the traction controls. So far, after 2.5 years and 36,000 miles, not one problem with it. Which is what keeps me in a Toyota, it is just so impressive how well they are built and how good their four wheel drive works!

[Edited on 4-15-2012 by David K]

Ken Cooke - 3-31-2012 at 03:54 PM

Quote:

Originally posted by David K

All 3 of my Tacomas had the rear locker, and while it sometimes takes a couple of tries to lock it, they all have worked.

Which is what keeps me in a Toyota, it is just so impressive how well they are built and how good their four wheel drive works!

My Rubicon only requires that I touch an on-off switch, and it locks (rear and/or front) instantly. Why doesn't your Toyota 4WD system have that ability? This is probably why an intermediate system like A-Trac was utilized, when your lockers cannot/will not activate.

Barry A. - 3-31-2012 at 04:11 PM

My Nissan X-Terra has an electric rear locker------it often is tricky to get it to engage---- or disengage for that matter. Gets a little frustrating at times, but eventually it does lock and unlock. Strange!!!! No "locking" or "unlocking" on the fly, or at least it never will for me unless I am lucky.

Barry

David K - 3-31-2012 at 06:13 PM

Barry and Ken... let's not confuse the Transfer Case (going into and out of 4WD) with locking differentials or A-TRAC, or any traction controls (limited slip)...

In a Tacoma: Going into H4 or back to H2 can be done moving (up to 60 mph) or stopped (sometimes a few feet of movement from stopped to fully engage or disengage)... This is because it (and your rigs I believe) have an ADD (automatic disconnecting differential).

Going from H4 (High Range 4WD) to L4 (Low Range) and back to H4 or H2 is done while stopped, in Neutral.

The traction control (called TRAC by Toyota) is automatic and on in H4, unless I deactivate it by pressing a button. The A-TRAC is on in L4, unless I deactivate it by pressing a button... easy. To deactivate either is to allow open differentials and tire spinning if desired. I find four wheeling in High Range with TRAC on and in Low Range with A-TRAC on much more impressive.

The rear locking differential is activated by pressing a button while stopped in L4, and sometimes takes a few feet of rolling to engage and disengage (the gear teeth need to line up for the locking key to insert).

The A-TRAC has taken me to Santa Maria and beyond without ever using the locker, and that was impressive... You did see how rough the Widowmaker was and how deep the bog was in the video clips, right?
I also used A-TRAC when I was climbing a hill and dropped into ruts so that both back tires were in the air... A-TRAC pulled my truck out. I turned the TRAC off in H4, on the beach in Baja, with tires at street pressure and burried it. I then went into L4 with the A-TRAC and the truck climbed out of the stuck without me getting out to clear away the sand first.

So, Ken... without pushing any buttons and just going into L4 on the transfer case selector, I have pretty near the same traction abilities as the Jeep Rubicon with front and rear electric lockers, but I don't have to turn off A-TRAC to make a tight turn, which with lockers... specially front lockers is less than easy.

I will agree that lockers are perhaps smoother, no lag or slip, and work great for the extreme. A-TRAC can seem jerky, allow some slipping before activating and makes noise when it is working... but it cost me nothing extra, and I am happy about that.

rts551 - 3-31-2012 at 06:19 PM

It cost you when you bought, whoops, leased the truck.... try the rock climbing trail and let us know how ou did.

David K - 3-31-2012 at 06:32 PM

It did fine, thanks... Yes, I always get an Off Road TRD 4WD Tacoma... primarily because that comes with a locking differential... the added bonus was the addition of A-TRAC in the Off Road Tacomas starting in 2009 (it has been in Land Cruisers, FJ Cruisers, other Toyotas and Lexus SUVs for many years).

4x4abc - 3-31-2012 at 08:44 PM

slow down guys - you are all over the place
sounds like 10 year olds taking about sex - lotsa enthusiasm, very little knowledge

the me start with lockable wheel hubs

wheel hubs have nothing to do with traction management or lockers - they simply connect or disconnect the wheels (can be front or rear) from the axle shafts - the same shafts that bring torque and rotation from the differential to the left and right:
http://4x4abc.com/4WD101/hubs.html

Ken Cooke - 3-31-2012 at 10:15 PM

Quote:

Originally posted by David K

The rear locking differential is activated by pressing a button while stopped in L4, and sometimes takes a few feet of rolling to engage and disengage (the gear teeth need to line up for the locking key to insert).

You have to completely stop your vehicle to activate your locking differentials? :!:

My Rubicon package cost an additional $4,000.00 - A little pricey, but a bargain that included;

Front/Rear Limited Slip Differentials (Full Time)
Front/Rear Mechanical Tru-Lok Locking Differentials (On-Demand)
Heavy Duty Rock-Trac "Super Low" 4:1 Transfer Case gearing
Fixed Yoke (not Slip Yoke)
Rocker Guards
Dana 44 (center section) axles

All the good stuff! :bounce:

For a mid-sized pickup truck, your TRD Tacoma is also a great package. It can be a challenge to move the lever-activated transfer case into position, but there are after market products that address this problem.

In 2003, I knew that I wanted a package that featured the above features included in one price from the factory - since I didn't have the extra $$ for modifications after losing so much money after modifying my Ford Ranger to perform like a Jeep. Yeah, right. :rolleyes:

I knew that had I purchased a Tacoma, a straight-axle conversion (w/coil overs) would be at the top of my list for modifications. A bit pricey, but it makes the Tacoma unstoppable, able to run a 35" tire. I plan on bolting on a set of 35" tires for my Rubicon sometime this summer.

[Edited on 4-1-2012 by Ken Cooke]

Ken Cooke - 3-31-2012 at 10:19 PM

Quote:

Originally posted by 4x4abc
slow down guys - you are all over the place
sounds like 10 year olds taking about sex - lotsa enthusiasm, very little knowledge

I have a thread for this: :lol:

Noche Gay (de Travesti) en Tijuana

4x4abc - 3-31-2012 at 10:21 PM

So, Ken, will I see you on the Rubicon with your Rubicon this summer?
You gotta show us what you can actually do with that dream machine

David K - 3-31-2012 at 11:16 PM

Ken all second generation Tacomas (2005+) have a dial that you rotate to engage the transfer case... for low range you also depress it while turning:

and you have indicator lights for each step...

Interesting that you can actually lock a differential while the gears are spinning?? Must have some kind of syncro in there?

For the Tacoma, you stop and push a button (RR DIFF LOCK):

Then if it doesn't click in, you move a bit and turn wheels a bit... until the light goes from flashing to solid:

4x4abc - 3-31-2012 at 11:48 PM

all diff locks are dog clutches

the will only engage when in the right position, for that there needs to be a difference in wheel rpm left to right

if there is a big difference in wheel rpm (one spinning tire) engaging the diff lock (forcing the two dog clutches together) will destroy the teeth of the locker

so, to avoid broken parts all manuals recommend to engage the locker(s) when the vehicle is either stationary or if moving, none of the wheels should have lost traction yet

sensitive drivers with experience can of course (at low engine rpm) still engage the locker(s) when wheel has lost traction. Since the dog clutch parts will move about 70 times slower (in case of the Rubicon) in low range than the engine rpm, they will engage slowly without causing damage.
Lets say your engine does 1000 rpm, then the wheels will rotate at 14 rpm. Even when slipping, the difference to the non slipping is minimal.

more here:
http://www.4x4abc.com/jeep101/engage-diff-lock.html
http://www.4x4abc.com/jeep101/engage-diff-lock.txt.html

so, if you want to engage you diff lock before getting to an obstacle and you are driving dead straight and the locker teeth are not lined up, the locker will not engage at all. However, if you would gently steer to one side (and one side only, do not go back and forth) a difference in wheel speed is achieved and the locker will engage.

Now what to do when you ant to turn the lockers off? Just pushing the button will only remove the force that put the teeth together. If there is an ever so slightly difference in wheel speed, the teeth are binding and will not disengage.
Here is what I do - I let go of my steering wheel for about 5 seconds. At 1 mph in low range no big deal. The engaged locker forces the vehicle to go dead straight and without a hand on the steering, no counter force is present - all 4 wheels rotate at the ame rpm and the locker teeth have enough play to disengage.

nuff rant

[Edited on 4-1-2012 by 4x4abc]

[Edited on 4-1-2012 by 4x4abc]

[Edited on 4-1-2012 by 4x4abc]

axle lock's

captkw - 4-1-2012 at 06:46 AM

btw, this design has been used in outboard gear cases since the late 50's..fact for the day.........K&T :cool:

Splain This about TRACTION CONTROL

durrelllrobert - 4-1-2012 at 07:28 AM

My GMC Yukon has a traction control system with an on-off switch on the dash. If I shut it off on a long raod trip (ie: Ensenada to Phoenix) I get an extra mile per gallon even though the highway is relatively straight most of the way. I have made this trip with the switch in both the on and off positions to verify this result. 18 mpg on/ 19 mpg off :?:

Traction Control ?????????????????

J.P. - 4-1-2012 at 08:11 AM

When i was a kid we had two pickups we hauled Hay with one was a Chevrolet stick shift the other was a GMC with a automatic other than the transmissons they were pretty much the same Truck. The stick shift stayed stuck in the SAND all the time. The automatic rarely ever got stuck.

David K - 4-1-2012 at 12:09 PM

Thank you Harald for the locker info. It agrees with what I experienced with the Tacoma. I guess Ken is lucky he hasn't destroyed his, engaging the locker while moving at regular speed! Unless there is a mechanism in the Rubicon Jeep that delays engaging until he has nearly stopped moving? With my locker, I can push the locker button while driving 20 mph, and the light will flash until it actually is engaged (and that happens when I have stopped or nearly stopped). It also flashes if the button is pushed in H4 or 2WD... but unless you perform the 'locker anytime mod', it only works in Low Range. The 2WD Off Road PreRunner Tacomas have the rear locker, and it naturally works in 2WD... so with the anytime mod, we fool the ecu into thinking it is in L4... when it isn't... at least that is what I think I read on Tacoma World? :?:

4x4abc - 4-1-2012 at 01:42 PM

Quote:

Originally posted by captkw
btw, this design has been used in outboard gear cases since the late 50's..fact for the day.........K&T :cool:

well, dog clutches have been around for a couple of centuries

here is a pretty wild setup at a mine (forgot where and when):

notice how rounded the teeth are from engaging at too high a speed difference

the setup had actually 2 dog clutches - the one on the left was used less often and still has square teeth:

Ken Cooke - 4-1-2012 at 04:59 PM

Quote:

Originally posted by 4x4abc
So, Ken, will I see you on the Rubicon with your Rubicon this summer?
You gotta show us what you can actually do with that dream machine

No, but you will see me with the title to the vehicle - no longer property of Bank of the West. :!:

ncampion - 4-1-2012 at 05:16 PM

Dog engagement is how all motorcycle gear boxes shift. Small, light gears change speed easily. Most off-roaders often shift without even using the clutch, just need to "unload" the gears for an instant.

4x4's explaination was perfect.

Barry A. - 4-1-2012 at 05:27 PM

4x4ABC----------------your post on "dog clutches" and how to engage and disengage our electric lockers is terrific, and answers all my questions. I have printed this out and put it in my owners manual (because I forget things) for future use.

I thank you very much.

Barry

Barry A. - 4-1-2012 at 05:30 PM

Quote:

Originally posted by ncampion
Dog engagement is how all motorcycle gear boxes shift. Small, light gears change speed easily. Most off-roaders often shift without even using the clutch, just need to "unload" the gears for an instant.

4x4's explaination was perfect.

Wow, speak for yourself "ncampion". I can do what you say and not use the clutch, but I almost never do it as it is very risky. For 30 years I drove a 4x4 vehicle off road professionally and never did what you say unless I was just showing someone that it could be done-----------if you screw up, bigtime wear on the gears, or worse.

Barry

rts551 - 4-1-2012 at 06:30 PM

I didn't know being a park ranger made you a professional driver.

Barry A. - 4-1-2012 at 07:03 PM

Quote:

Originally posted by rts551
I didn't know being a park ranger made you a professional driver.

Hmmmmmmmmm, Well, maybe a stretch. But I spent most of my career in the desert, and we drove 4x4's in the dirt almost every day, so I thought that it qualified me to say that--------. :spingrin:

Maybe a better claim would be "an experience 4-wheel drive veh. operator which was a large part of my job". :yes:

Barry

David K - 4-1-2012 at 07:11 PM

Quote:

Originally posted by Ken Cooke

Quote:

Originally posted by 4x4abc
So, Ken, will I see you on the Rubicon with your Rubicon this summer?
You gotta show us what you can actually do with that dream machine

No, but you will see me with the title to the vehicle - no longer property of Bank of the West. :!:

Congratulations Ken! :bounce:

Still no answer to my previous post

durrelllrobert - 4-15-2012 at 08:21 AM

Doesn't anyone have a possible answer to why my Yukon gets better mileage with the traction control turned off? If you think I'm fullasheet I will accept that too.

TMW - 4-15-2012 at 08:43 AM

While the road may look straight it is not. You are always turning left and right ever so little. With the traction control turned on it senses that little difference and appies the brake to the wheel going faster. You don't feel it because it does it so quick and lightly. Think of it this way a house light bulb appears to stay lit when AC power is applied. But the AC current is going from positive to negative 60 times per second, too fast for the eye to see. If you slowed the cycle down to 1 cycle per second you would see the light get brighter then dimmer back and forth.

David K - 4-15-2012 at 11:38 AM

On my traction control, the anti-spin (limited slip) only comes on after there is some spin so it allows the diff. to remain open (no brakes applied) until you have lost traction and the tire breaks free and spins for a moment. Now, I am not saying the Chevy Yukon uses the same technology as the Toyota Tacoma... but surely it isn't constantly breaking for tiny steering changes??

Maybe I will turn off my traction control next time I fill upm and see if there is any change? I hope not to find out I could gain 1-2 mpg after 2 years of loving it... specially on wet days! It sure improves the 4WD when off roading!

Skipjack Joe - 4-15-2012 at 12:34 PM

David,

I've enjoyed this thread so much. I've learned so much about my own tacoma which the manual never made clear.

I thought that when I was putting it 4wd lo I was automatically getting the locking differential. Even though the button wass clearly there. I did experiment with the locking without understanding what it did. I would press the button and nothing happened. No lights came on, nada. I just gave up.

Have an 04 Tacoma.

My question is: Under what natural circumstances would I need i need this.

Is this primarily for the Ken Cooke rock climbing stuff?

I have been driving over sand in 4wd without problems. Have climbed steep hills as well. Would it help in getting out of mud? I avoid mud.

David K - 4-15-2012 at 12:43 PM

Quote:

Originally posted by Skipjack Joe
David,

I've enjoyed this thread so much. I've learned so much about my own tacoma which the manual never made clear.

I thought that when I was putting it 4wd lo I was automatically getting the locking differential. Even though the button wass clearly there. I did experiment with the locking without understanding what it did. I would press the button and nothing happened. No lights came on, nada. I just gave up.

Have an 04 Tacoma.

My question is: Under what natural circumstances would I need i need this.

Is this primarily for the Ken Cooke rock climbing stuff?

I have been driving over sand in 4wd without problems. Have climbed steep hills as well. Would it help in getting out of mud? I avoid mud.

The rear locker is best used to get out of any situation the normal 4WD low doesn't get you through... or over.

I mainly used mine for STEEP, uneven roadbed, grades... Any deep ruts, big rocks or situations that one tire would be in the air. Without the rear locked, that one tire would spin... When locked, both rear tires rotate the same... so you move ahead if the front end is in bad stuff and has no traction.

Out of mud, sure... it sure is better to have both back tires turning instead of just one!

Practice engaging it... Go into L4, then press the locker button... As you begin to move ahead, the flashing light should go solid. If not, turn your wheel one direction and move slowly.

TMW - 4-15-2012 at 05:03 PM

Traction control works the same on all vehicles. When the wheel sensor on any wheel shows any wheel going faster than the other wheels it applies the brake to that wheel. If you are going around a curve the outside wheels will go faster than the inside wheels and thus apply the brake to the outside wheels. Now how fast and sensitive the system is on a particular brand may be another question. Turn on your traction control and drive it over any road course especially where there are curves and I'll bet your gas milage is less.

TMW - 4-15-2012 at 05:17 PM

Quote:

Consider this you are going up a hill to join a cross road and when you get to the top as you cross over the right front wheel comes off the ground and the left rear also comes off the ground, not much but enough to not have any traction with the ground. What would happen. The wheels without traction would spin and you would not go anywhere. I've had this happen going into Mikes Sky Ranch several years ago from the west. If your rear wheels are locked you would have traction with the rear wheels and would still move over the top. Normally in a 4 wheel drive vehicle having a locker doesn't matter but in some cases it will it just depends on the circumstances. Rock crawlers like both the front and rear locked so they can crawl over the rocks at slow speeds. Some 2 wheel drive racers just weld the rear so it's just a solid axle like an ATV. It's hard on tires but so what it just for racing. If I had a Toyota rear locker that only worked in 4x4 low I'd modify it to work in 4x4 high. I don't often use 4x4 low but I do like my rear locked when off road.

[Edited on 4-16-2012 by TW]

chuckie - 4-15-2012 at 05:42 PM

I noticed that my second exwife often locked her rear end when we went off road in Baja....

Skipjack Joe - 4-15-2012 at 06:08 PM

When I place the 4wd in lo. The rear wheels no longer turn evenly during the turns. One skips the earth to stay with the other. I assumed this phenomena was due to the differential being locked. I never thought to look that the rear don't spin faster than front. That all wheels potentially get equal traction.

Was the locking diferrential engaged or not?

As I understand it if I stall my vehicle in sand with a wheel spinning I can get out with a locking differential by having it spin no faster than what the front is trying to do. I see this as helping because it stops from burying deeper?

So the rr locking differential locks the rear but not the front? Confusions reigns in light of earlier discussion.

[Edited on 4-16-2012 by Skipjack Joe]

durrelllrobert - 4-15-2012 at 06:18 PM

Quote:

Originally posted by chuckie
I noticed that my second exwife often locked her rear end when we went off road in Baja....

Fernweh - 4-15-2012 at 08:32 PM

Quote from the Battle at Waterloo:

"I wish it would be already night and the Prussians are coming"

4X4abc where are you? We need you to clarify this 4x4 or not to be......

4x4abc - 4-15-2012 at 08:54 PM

Quote:

Originally posted by TW
Traction control works the same on all vehicles. When the wheel sensor on any wheel shows any wheel going faster than the other wheels it applies the brake to that wheel. If you are going around a curve the outside wheels will go faster than the inside wheels and thus apply the brake to the outside wheels. Now how fast and sensitive the system is on a particular brand may be another question. Turn on your traction control and drive it over any road course especially where there are curves and I'll bet your gas milage is less.

excuse my English here, Sir! But that's BS. Pure BS.

If traction control would slow down the outside wheel during a turn, you would be forced to to drive straight.

The engineers are not that stupid. The wheel speed differences during a turn are tolerated without traction control interference.

Only wheel speed differences created by traction loss will trigger traction control - and sometimes stability control at the same time.

David K - 4-15-2012 at 08:58 PM

Quote:

Originally posted by Skipjack Joe
When I place the 4wd in lo. The rear wheels no longer turn evenly during the turns. One skips the earth to stay with the other. I assumed this phenomena was due to the differential being locked. I never thought to look that the rear don't spin faster than front. That all wheels potentially get equal traction.

Was the locking diferrential engaged or not?

As I understand it if I stall my vehicle in sand with a wheel spinning I can get out with a locking differential by having it spin no faster than what the front is trying to do. I see this as helping because it stops from burying deeper?

So the rr locking differential locks the rear but not the front? Confusions reigns in light of earlier discussion.

[Edited on 4-16-2012 by Skipjack Joe]

RR means rear... Toyota has no front locker on Tacomas or any other North American vehicle. The locker is an electric motor attached to the differential. More later, I need to run!

4x4abc - 4-15-2012 at 09:08 PM

Quote:

Originally posted by Fernweh
Quote from the Battle at Waterloo:

"I wish it would be already night and the Prussians are coming"

4X4abc where are you? We need you to clarify this 4x4 or not to be......

Karl,

I can't really help in this case. It's going all over the place.
Traction control, gas consumption, locked up rears, differential locks, traction, spinning tires, low range, questionable observations, nobody knows what he is talking about - my head is spinning.

Need traction control for my head
a few drinks will do
Going for Margaritas now.
With those 2 stunning Mexican girls
just came back from the beach with them
sunshine, Champagne and prosciutto - divine!

don't care about lockers and/or traction control

Ken Cooke - 4-15-2012 at 09:43 PM

I believe that I have some old copies of FOURWHEELER and 4 Wheel and Off Road to loan to TW. The 4WD magazines explain traction-aided differentials every 2-3 years.

Fernweh - 4-15-2012 at 09:59 PM

Quote:

Originally posted by 4x4abc

Quote:

Sorry to hear this.....

Please don't rub it in, with the beach and so....

Harald, thanks for the picture. Which one is the stunning one?

You drink Champagne with lime? Strange.....

TMW - 4-16-2012 at 10:00 AM

Quote:

Originally posted by 4x4abc

Quote:

If what I said is BS then explain why he gets better gas mileage when it is turned off. I still say it's because the system is applying the brakes.

David K - 4-16-2012 at 10:21 AM

All new Toyotas have traction control (TRAC) and stability control (VSC, from Bosch) that use the computer and ABS brake system to a) help you get moving in slippery conditions and b) help you stay driving straight ahead when you vehicle wants to go into a spin-out.

Since fuel economy is all important now, it would surprise me if TRAC turned off provided better mileage, but I am willing to try that. By pressing the VSC Off switch for about 5 seconds (while stopped), you can turn off VSC and TRAC. This must be done after anytime the car has been turned off. VSC will come back on automatically if the system senses you are about to spin out or wreck your car. Those Germans at Bosch are some smart people! VSC has been called the greatest safety device since the seat belt...

As for traction aid, the difference between my '05 and '10 Tacomas is like night and day... The '10 with TRAC limited slip on all 4 tires makes my truck easily go beyond where my previous one would need either deflating the tires or going in low range with the locker on.

[Edited on 4-16-2012 by David K]

mtgoat666 - 4-16-2012 at 10:36 AM

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Originally posted by 4x4abc

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vehicle stability control is noticeable when it engages. in my toyota 4runner, you can hear/feel brakes engage when stability control takes over, and it very rarely engages when driving on pavement. it often engages off road where tires experience differential slip, but can be disengaged in certain 4wd settings.

you all are wrong to think it engages brakes of outside wheel when doing normal cornering on paved street.

David K - 4-16-2012 at 10:40 AM

"you all are wrong to think it engages brakes of outside wheel when doing normal cornering on paved street. "

All ??

I know it doesn't do that... The brakes are only used after a tire spins to limit the slip, or to straighten the vehicle if it is sliding out of control.

Taco de Baja - 4-16-2012 at 11:01 AM

Quote:

Originally posted by David K
All new Toyotas have traction control (TRAC) and stability control (VSC, from Bosch) that use the computer and ABS brake system to a) help you get moving in slippery conditions and b) help you stay driving straight ahead when you vehicle wants to go into a spin-out.

This "stupid" traction control's only purpose seems to be to annoy the driver and passengers by insistently beeping to indicate that the tires are spinning when going up a sand wash. :rolleyes:

My all manual 1996 Tacoma (front hubs, transmission, and t-case) with open differentials, does just as well in the washes without the "beep-beep-beep, beep-beep, beep, beep-beep-beep." :lol:

TMW - 4-16-2012 at 11:10 AM

I don't know how sesitive these systems are. Maybe the better gas mileage is because of a problem and maybe it's too sensitive when on. I do know the traction control on the Yukon applies the brakes so to me it stands to reason that with it on and he gets less gas mileage it must have something to do with the brakes. I have reached out to GMC and asked them to explain why and when I get an answer I'll post it.

David K - 4-16-2012 at 12:14 PM

Quote:

Originally posted by Taco de Baja

Quote:

This "stupid" traction control's only purpose seems to be to annoy the driver and passengers by insistently beeping to indicate that the tires are spinning when going up a sand wash. :rolleyes:

My all manual 1996 Tacoma (front hubs, transmission, and t-case) with open differentials, does just as well in the washes without the "beep-beep-beep, beep-beep, beep, beep-beep-beep." :lol:

Yah, I know... you either get used to it, disable the beeper, or turn off the traction control (but then you can't drive in the sand as easily without deflating).

Ken Cooke - 4-16-2012 at 04:29 PM

Quote:

Originally posted by David K
VSC will come back on automatically if the system senses you are about to spin out or wreck your car. Those Germans at Bosch are some spart people! VSC has been called the greatest safety device since the seat belt...

As you know, I drive a Honda Pilot to work and to the grocery store or restaurant when the Wife is riding with me. Although, it is a front wheel drive vehicle, it also has some sort of Vehicle Stability Control system. When you try to get the slightest bit wild on sand or dirt, the system kicks in, and applies brakes here, and slows you down. Now, I'm a responsible driver, but that takes all of the fun out of any spontaneity I might be after.

Why, then is VSC a good thing on an off-road driven, 4WD vehicle?

Can this be completely defeated by pulling a fuse in order that you can enjoy some real fun? (i.e. - The Dunes) :?:

Taco de Baja - 4-16-2012 at 04:45 PM

Maybe all this auto braking explains the $1,000 brake job my sister needed on her FJ-Cruiser with 30,000 miles to replace the rotors and pads at the Toyota Stealership. :rolleyes:

Not under warranty, BTW.

Ken Cooke - 4-16-2012 at 04:54 PM

Quote:

Originally posted by Taco de Baja
Maybe all this auto braking explains the $1,000 brake job my sister needed on her FJ-Cruiser with 30,000 miles to replace the rotors and pads at the Toyota Stealership. :rolleyes:

Not under warranty, BTW.

Not under warranty??? My Rubicon had a 30,000 mi. bumper to bumper warranty (in '03). My rotors and pads on the Rubicon are both original - the pads need replacement, but the rotors are in decent shape with 125,000 original miles.

David K - 4-16-2012 at 04:55 PM

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Originally posted by Ken Cooke

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1) Safety First (as Americans are sue happy)... it applies brakes for only milli seconds to keep you from spinning out, not to 'slow you down' (at least in a Toyota).

2) You should have a button to turn off the VSC and traction control (Toyotas do).

3) By limiting slip, power diverts to the tires with traction instead of spinning a hole.

I tested my truck at Bahia Santa Maria when it was just a month old (in front of Rob and Connie's). First thing I did was drive onto the beach (dry sand above the high tide line, in front of their house) with the tires at 32 psi. In the past, I would be limited as to how far I could go with momentum before digging in.

This truck, with traction control, didn't dig in... I could stop and go on the deep sand.

To see if this was some weird condition and not the traction control, I turned the TRAC (traction control) off and tried to drive in 4WD-HI with open differentials only... and I went about 15 feet and got stuck... no more forward motion stuck.

To try and get out of the stuck without digging or letting any air out of the tires, I tried the A-TRAC device (Active Traction Control), in low range... which is Toyota's super traction system that can be best described as 'automatic lockers front and rear'. I was able to drive out of the stuck, then I returned to high range with TRAC once again back on, and continued to drive with ease.

So, with the new truck on a bottomless sand beach, I was amazed by TRAC and A-TRAC the same day.

As a follow-up, the next time down, the weather was hotter and I had a heavy load of camping gear, going onto Shell Island... and I did have to air down. So weight in the truck and perhaps higher sand temerature dictates needing to air down.

David K - 4-16-2012 at 04:57 PM

Quote:

Not under warranty, BTW.

That is just crazy, I do have the dealership work on my truck, and a full front brake job (new rotors and pads) was under $300, as I recall. I would question what else was done and she can easily contact the district manager for false charges.

David K - 4-16-2012 at 05:04 PM

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Originally posted by Ken Cooke

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Not under warranty, BTW.

Ken, brakes and oil changes are normal maintenance items that are not warranty... Unless the brakes were bad, noisy, shakey, etc.

The Toyota has a 3 year/ 36,000 mile bumper to bumper warranty and a 60,000 mile drivetrain warranty. My truck has just passed the 36,000 mile mark, and there has been not one warranty issue/ part failure, etc. after the drip that was fixed when the truck was brand new (Toyotas aren't supposed to drip a thing other than AC water)!

You have seen how hard I am on the truck (all three of my Toyotas)... and the quality control and strength of parts used is nothing short of amazing... specially when compared to other brands.

[Edited on 4-17-2012 by David K]

NEW IS NOT BETTER!

Ken Cooke - 4-16-2012 at 05:11 PM

But, how are your brakes holding up with all of that traction assisting you have going on?

This Toyota did great with simple positive locking differentials. Very cool, vintage truck as well!

No VSC in Colombia (just trouble for our troops and Secret Service!) :lol:

VSC and ATRAC were not options when this Ambulance was made.

Snorkel, check.
Stock winch-mount bumper w/8,000# winch, check.
Solid front axle - no Inferior Front Suspension (IFS), check.
Built and ready for Baja, check.
VSC/A-TRAC traction sensing control, NOT!

VSC/A-TRAC, check
Air Conditioning, check
Four doors, check
Low water-line clearance/short breather tubes, check.

David K - 4-16-2012 at 05:42 PM

Running boards are not recommended where I take my Tacoma... No matter if that is a Toyota Hilux or not!

Ateo - 4-16-2012 at 06:13 PM

First time I heard that "beep-beep-beep, beep-beep, beep, beep-beep-beep" sound in my tundra it scared the crap out of me. I was just outside of Datil with a 2 week old truck wondering if that warning was telling me I was about break down or something. "Honey, get out the owners manual and tell me what 'auto LSD' means - Am I about to be dosed with LSD?". Fortunately it was just some loose sand.....

David K - 4-16-2012 at 06:20 PM

Quote:

Originally posted by ateo
First time I heard that "beep-beep-beep, beep-beep, beep, beep-beep-beep" sound in my tundra it scared the crap out of me. I was just outside of Datil with a 2 week old truck wondering if that warning was telling me I was about break down or something. "Honey, get out the owners manual and tell me what 'auto LSD' means - Am I about to be dosed with LSD?". Fortunately it was just some loose sand.....

We were with BajaRob and Connie, trying to find some fossil beds south of San Felipe in my new Tacoma... and in the sand washes, fish tailing around (good fun), the VSC was doing the beep-beep beep... like it was telling me (as in HAL in 2001 A Space Odyssey): "What are you doing Dave?", "Perhaps you should re-think your driving style Dave?" :lol:

Ken Cooke - 4-16-2012 at 06:50 PM

Quote:

Originally posted by David K
and in the sand washes, fish tailing around (good fun), the VSC was doing the beep-beep beep... like it was telling me (as in HAL in 2001 A Space Odyssey): "What are you doing Dave?", "Perhaps you should re-think your driving style Dave?" :lol:

Sorry, but that would just drive me crazy. Don't the TTORA guys have a bypass for that? Perhaps a fuse which can be pulled out in order to avoid this noise?

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