BajaNomad - 4WD vrs AWD - Powered by XMB

4WD vrs AWD

alafrontera - 11-28-2009 at 10:09 AM

Not sure where to ask this, not really an "off-roading" question. Figured the gearheads might read this forum

I have two all wheel drive vehicles, a Chevy Astro van and a Suburu Impreza. I have never found a clear explaination of exactly what this means. How does it differ from four wheel drive? Neither vehicle has a low gear range and they are permanently in AWD, you can't shift out of it.

I plan to use the van for camping and just wonder how much benefit I will get from the AWD. Also I plan to use the car for day trips or or overnights to Ensenada and thereabouts.

I also have a 4WD Dodge Ram 1500 but really prefer to use the van or car.

BajaGringo - 11-28-2009 at 10:15 AM

AWD is in all wheel (4 wheel) all the time. 4 wheel drive is only in 4 wheel drive when shifted by you or the vehicle. I have both - my Yukon is 2/4 wheel drive and shifts into 4 wheel drive automatically when it senses it has lost traction in 2 wheel drive. My ML350 is AWD and gets no better gas mileage than my big 8 cylinder GMC. With the added weight and power the Yukon has I have more faith in it to get me out of a bind than the Mercedes...

YMMV

woody with a view - 11-28-2009 at 10:26 AM

most cars have engine power to only 1 wheel. my tundra has a limited slip rear differential so when one rear tire starts spinning the other rear tire engages and get traction. when the 4wd button is pushed i then have 3 tires getting traction, unless the one rear starts spinning, then all 4! i could be wrong!

AWD is what it states, all wheels all the time = crappier gas mileage.

[Edited on 11-28-2009 by woody in ob]

bigboy - 11-28-2009 at 11:58 AM

Woody,
All open differentials apply equal torque to both wheels at all times. Go to, how stuff works, for a detailed explanation!

Just imagine if you disconnected one brake line to the driving axle and tried a panic stop. It's the same for hard acceleration.

TMW - 11-28-2009 at 12:04 PM

As said, AWD means all four wheels are drive wheels. The differentials are not locked however. AWD does not have a low range. 4WD is usually refered to as Part Time 4WD. It is not recommended to stay in 4WD like a long trip on pavement. When in 4WD it is harder to turn on hard pavement like concrete etc, especially if the front has a locking differential. 4WD usually has a low range for sand and snow. Low range allows you to keep the RPMs up and not bog down and less chance of spinning your wheels. AWD is better than 2WD for rain and snow. Because it drives all the wheels it will not get as good gas milage as say the same vehicle in 2WD. AWD vehicles tend to be smaller or at least have smaller tires and I think that is why when turning they do better. You find 4WD in vehicles that have larger tires especially trucks and bigger SUVs like the Tahoe.

jack - 11-28-2009 at 01:46 PM

TW explains it all very well. A real 4 wheel drive enthusiast does not like AWD because there is no low range, but for most people they won't even miss it. The big advantage to AWD (especially in winter) is when you go from good traction on a road to no traction, like when you hit black ice. A part time 4WD should not be in 4WD and driven on dry pavement or damage to the system may occur. By the time you realize your on black ice it may be too late for someone with a part time 4WD to shift into 4WD, they may already be in the ditch.

comitan - 11-28-2009 at 01:56 PM

alafrontera

I have the Astro Van AWD and love it, it only goes into AWD when one tire slips, and contrary to belief I know that all the tires are NOT
working when stuck, I have had this Vehicle 4 years and have been everywhere in it, only stuck bad once deep,deep soft sand and high centered. One other thing my gas mileage for the last 9,000 miles is 15.8 that includes many hours at the border and city driving. Actually the computer reads as high as 22MPG when doing 70MPH on the freeways.

[Edited on 11-28-2009 by comitan]

BajaGringo - 11-28-2009 at 01:57 PM

Quote:

Originally posted by TW
AWD does not have a low range.

My AWD ML350 has a low range that can be engaged electronically...

Barry A. - 11-28-2009 at 02:52 PM

Just to confuse the issue :lol:

---------being in 4 wheel drive on ice without studded tires, or chains, can get you in trouble really fast as it often causes all 4 wheels to lose traction simultaneously---------zip, off the road you go.

In the Colorado Rockies we usually kept our trucks in 2-wheel drive whenever possible to prevent that from happening. The old posi-traction causes the same phenomena, as do "lockers". Personally, I would only use any of the "switchable" systems on ice as a last resort to get you out of a bad situation, but I admit I don't fully understand the new systems.

IF, and I really don't know, the AWD vehicle really has power to all wheels at the same time, you could be in trouble really fast on ice if you don't have studded tires, or chains, for the reasons laid out above..

Barry

TMW - 11-28-2009 at 03:21 PM

Barry reguarding positraction that is why GM when to a limited slip or whatever they call it, where it unlocks above 25 mph. A lot of emergency vehicles when they hit ice on one wheel with positraction would spin out. I think most AWD vehicles apply the break to the wheel that spins. But that may only apply to vehicles with traction control.

Anytime I drive in snow and especially ice I put the chains on. Too many close calls in the mountains. It's a long way down.

Barry A. - 11-28-2009 at 04:01 PM

Quote:

Originally posted by TW

Anytime I drive in snow and especially ice I put the chains on. Too many close calls in the mountains. It's a long way down.

Yes, and if chains are installed properly, with "chain tighteners" (big rubber bands), you can drive for 100's of miles on them without ruining the chains. In many cases, where the snow never left the roads for months (Glacier Natl. Park, MT), we left them on all the time. I once (winter of 67/68) drove on chains from Cedar City, UT to almost the Canadian border in Montana (West Glacier) (hauling a trailer) without doing much damage to the chains---snow pack all the way! Chains work, and work well.

Barry

Baja12valve - 11-28-2009 at 04:20 PM

I can't say too much about AWD as I don't have one. I do know that they don't have a low range, but in many instances, low range is not necessary. Having a AWD on any dirt road would be a benefit. I ALWAYS put my truck in 4wd on dirt roads. It handles about 100% better, stops better, steers better and takes the washboard better. A world of difference.
Open differential, the cheapest, least effective one out there. It will give equal power to both wheels until one loses traction, then it gives all power to that wheel. Very easy to get stuck. So if you get stuck with a open diff and you stuff wood and rocks under the spinning wheel, the other wheel may start spinning. In low traction situations like sand, snow, mud, it can be a real hassle.
Positraction. Much better. Again, power to both if equal traction, but if one starts spinning, the power transfers to the one that is not spinning. You still have one wheel drive, just the one with the traction. With a clutch type positraction, the most common, you can arrange the clutches to increase the torque transfer. I can jack up my truck and put blocks under the frame, lifting three wheels off the ground. The remaining one will pull the truck off the blocks. The wheel in the air, opposite the grounded wheel will not spin. I can do this with both the front and rear. If I do a burnout, I will put down two strips of rubber. I can't quite get all four wheels to spin on dry pavement.
Locking. Gives equal power to both wheels regardless of traction. If one is on the ground and one is in the air, both spin at the same speed with the same amount of power and torque. The best arrangement for pure traction. Having a locker in the front can create some very bad handling manners, like a real lack of steering. If you have one in the rear, in the rain, snow or ice, you can spin out real easily because the locker will sense one wheel losing grip as you go around a corner, lock up the other one, now both are spinning at the same speed, bye bye. I think the new selectable e-lockers are far better than the automatic ones.
Each differential has pluses and minuses depending on how you use 4wd and the type of terrain. I think that open differentials are worthless.

Barry A. - 11-28-2009 at 05:02 PM

baja12valve said-------" Having a AWD on any dirt road would be a benefit. I ALWAYS put my truck in 4wd on dirt roads. It handles about 100% better, stops better, steers better and takes the washboard better. A world of difference."

Hmmmmmm---I have not had that experience. To me the vehicle becomes much more squirrley on washboard and sandy roads when in 4-wheel drive at any speed above about 20 mph. I NEVER put my vehicle in 4-wheel drive unless I can't progress without it. Different strokes for different folks------ :yes:

Barry

woody with a view - 11-28-2009 at 05:07 PM

Barry

try it next time you're on a bad washboard. it SEEMS like the truck pulls itself over the washboard=smooth, instead of pounding into each rut.

[Edited on 11-29-2009 by woody in ob]

Barry A. - 11-28-2009 at 05:12 PM

Quote:

Originally posted by woody in ob
Barry

try it next time you're on a bad washboard. it SEEMS like the truck pulls itself over the washboard=smooth, instead of pounding into each rut.

[Edited on 11-29-2009 by woody in ob]

Well, that would make sense under certain circumstances I suppose, such as excellerating much of the time. My conservative driving probably does not take advantage of that factor, and maybe that explains it. Sure feels squirrley to me. I hate washboard!!!

Next time I will give er a try-------------thanks.

Barry

Baja12valve - 11-28-2009 at 05:22 PM

Quote:

Originally posted by woody in ob
Barry

SEEMS like the truck pulls itself over the washboard=smooth, instead of pounding into each rut.

That is what I feel. The front wheels are powered over the ruts and bumps instead of being pushed over them by the rears. I air down to 30 psi and I don't even notice washboard roads, I can drive over them at any speed I want. I don't know what it is, but I have never been in any vehicle that handles washboards as well as my truck.

ncampion - 11-28-2009 at 06:00 PM

The main difference between 4WD and AWD is that in 4WD the transfer case is used to lock the front driceshaft and the read driveshaft together thus applying the same torque to each set of wheels. It usually incorporates a low range gear set for extra torque when necessary. There is no "slippage" between front and rear. This gives ideal tracton when off-road or on other poor traction surfaces. It should not be used on good tracton roads (e.g. dry pavement) as it will rapidly wear tires and cause poor gas mileage. It is also manually turned ON or OFF.
With AWD, the transfer case is always engaged, but it does not "lock" the driveshafts together, rather it uses either a viscus coupling or some kind of open differential which allows the front wheels to turn at a different speed that the rears if necessary. The more sophisticated systems also allow a different percentage of torque to be applied to the fronts vs. the rears. This is up to the car maker. AWD is "always on" and generally does not incorporate a low range gearset, but may. AWD is not necessarly designed to provide traction for off roading, but as a performance and handling feature on dry pavement. It does however provide some additional traction control on bad traction roads.
AWD is better than 2WD and 4WD is the best for serious off road use. I won't even get into the subject of differentials at this point, that's a whole other issue.

woody with a view - 11-28-2009 at 06:23 PM

my toyo at's say on the sidewall to run at 32??????????????????? i run em at 40 for everyday driving. last time down the beach was at 15--18 and the tundra even pulled an F350 4 door 4x4 outta the soft stuff. :rolleyes:

tripledigitken - 11-28-2009 at 08:09 PM

I try to engage my "part time" four wheel drive every time it gets in the dirt, if only for a few miles, to lubricate the gears. Not engaging it unless you really need isn't necessarily a good thing.

Ken

Barry A. - 11-28-2009 at 11:09 PM

Ken, yes, I do that too, and for the reason you cite. Always a good idea to stir up the lubricants in the diff.. etc. when off the pavement.

I am going to try the 4-wheel drive engaged thang next time on big washboard----but I am still dubious.

Barry

woody with a view - 11-29-2009 at 02:03 AM

Quote:

Originally posted by Barry A.
Ken, yes, I do that too, and for the reason you cite. Always a good idea to stir up the lubricants in the diff.. etc. when off the pavement.

I am going to try the 4-wheel drive engaged thang next time on big washboard----but I am still dubious.

Barry

Barry

this is a reason for you to head south and get off the black top..... if for some reason you need a strip of dirt to sample, PLEASE let me G'know! i'll get you onto some fancy clay trails.

Baja12valve - 11-29-2009 at 10:35 AM

I am going to try the 4-wheel drive engaged thang next time on big washboard----but I am still dubious.
Barry [/quote

It will be better, not perfect, but better. On washboard remember that the wheels are spending as much time in the air as on the ground, so the handling will be squirrelly no matter what. It is with me. I find the truck "floating" and not as surefooted, but I still find it to be much better in 4wd vs. 2wd. Lower tire pressure and speed helps a lot, but I still do 40+. Stiff suspension is a bummer, all you do is rattle yourself to death. Larger diameter tires help, they roll over stuff better. Maybe my weight helps, I don't know, but with my camper shell on, fully loaded, I push 8,000 lbs. Every vehicle set up is different, where I may shine, in other areas I don't. My truck is no sand buggy.

David K - 11-29-2009 at 10:56 AM

Barry, there is a difference in handeling when in 4WD at speed on a graded/ washboard road... It is much more secure when in 4WD... Really feel the difference!

AWD... remember, there are FULL TIME 4WD syatems out there like Quadra Trac from Jeep, that are not the same as AWD... Then there are the really sophisticated systems from Mercedes and Range Rover that have differencial selection, etc.

AWD also does not mean all 4 tires get power all the time... it means all up to all 4 can receive power, when needed for traction... Subarus and Audi Quattros were some of the first AWD automobiles. Originally Subaru was the first passenger 4WD (1975ish), then added low range... then dropped 4WD for the AWD system they offer (no low range). American Motors offered the Eagle 4WD cars after Subaru.

Today's 4WD trucks and SUVs offer the convenience of shift on the fly 4WD from inside the cab (part time 4WD) so you are in economic 2WD until you need 4WD. With automatic locking hubs, no need to get out and perform that task either. AWD or full time 4WD vehicles, no need to shift into anything. The car senses any wheel that looses traction and transfers the power to wheels with traction.

FOR BAJA backroad driving: 4WD trucks or SUVs would be the wiser choice, as they will have better ground clearance for rocky roads and will likely have low range for any steep grades or tough conditions where slow, power crawling is needed. 4WD is made for off highway driving.

AWD is a superior handling traction system for cars on paved or wet/ icy/ gravel or graded roads... It should be fine in the sand with air pressure lowered, but I would avoid any non-graded roads if you choose AWD for Baja because of ground clearance.

toneart - 11-29-2009 at 11:31 AM

My experience is with a Ford F150 4WD, so I cannot compare with AWD. My neighbor has a Saturn with AWD and he says it handles better in snow and ice than 2WD.

When in the Northern Ca. mountains and in Baja, I drive on pavement and then hit long stretches of dirt roads. I am not off-roading per se, so I keep the tires inflated for highway driving...around 36-41 PSI.

When on the dirt roads I encounter different kinds of road surface; washboard and/or potholes with rounded edges (usually not the axle breaking kind you get with pavement), and sometimes deeper sandy areas. I put it into 4WD and it is always a smoother ride. I get better traction. Not so much slipping and sliding around. The washboards are still bumpy, but they seem less so in 4WD.

Where 4WD really comes in handy is in snow. I get better traction. The main safety factor is to drive very s-l-o-w-l-y in icy conditions. You are no safer in 4WD when you hit a patch of black ice. The key is to go slowly enough and anticipate the ice. Having your vehicle under control is much easier when driving slowly. I have seen too many young "hot dogs" who pass you under dangerous conditions and then they end up in a head-on collision, smashed into a tree, or over an embankment.

TMW - 11-29-2009 at 11:34 AM

I always use 4WD when I get off the pavement for any distance. I think it handles better especially on sand roads. Another reason is when in 2WD there is more of a tendency for the rear wheels to spin and with some of the roads I've encountered in Baja the rocks can be sharp causing damage to the tires. 4WD less chance to spin the tires.

Barry A. - 11-29-2009 at 02:44 PM

How can allllllllllll you people refute my sage and learned advise on driving back country roads???? How embarrassing!!! :wow:

I except the challenge (despite knowing that it is all bunk) and will try and impliment your advice next time out and about--------if you are right, you probably will NEVER hear me admit it (unless bribed)

If I am RIGHT, then you will definitely hear about it----------- :lol:

Whoooo ahhhh!!!!

Barry

Baja12valve - 11-29-2009 at 03:12 PM

No worries. If we hear nothing, we know we are right, your silence will speak volumes, LOL!!! :biggrin:

David K - 11-29-2009 at 06:58 PM

Barry, you got there and back home the way you did, just fine... no worries!

With the newer shift-on-the-fly 4WD we have, it is easy to be driving 40-50 mph on a sandy, washboard road and click it into 4WD from 2WD and notice the difference in handeling, right away. You get a superior feel of control over your truck when it is in 4WD... less drifting or sliding.

Barry A. - 11-29-2009 at 07:09 PM

-------thanks guys, and bottom line is that "less drifting and sliding" is what we are all after.

Possibly my problem is that both my Baja proven rigs are solid axle old style 4x4's ('94 Ford F-250 & '89 Isuzu Trooper--both stick shift). Even my 2007 X-terra Off-Road model does not have all the fancy new stuff on it, I don't think.

Thanks for keeping me honest. I need to drive one of these newer high-tech machines, I suppose.

Barry

Baja12valve - 11-29-2009 at 08:09 PM

I would not be so quick to blame or diss the old solid axle set-up. Mine is that way, 96, solid axle Dana 60, stick shift. It works outstanding on washboard roads. I think that suspension and tire combinations are very important in how the vehicle, any vehicle, will handle. I have in-cab adjustable shocks. On washboard or semi-smooth dirt I make it as soft as possible allowing the wheels to travel when they hit something instead of thumping over it. As I mentioned earlier, stiff suspension is a bummer.
My friend has the Off-Road X-terra and stock, he has the Eaton electric locker on the rear. The front is independent, but the differential is a open.

BajaGringo - 11-29-2009 at 08:15 PM

Another factor is weight over the rear axles. Pickups tend to get less traction from the rear wheels than SUV's - the added weight really does make a difference...

Neal Johns - 11-29-2009 at 08:51 PM

Uh, woody in ob,
The Psi on the tire sidewall is the Maximum safe pressure for that tire (determined by the manufacturer), not the recommended pressure. The recommended pressure (for the tire supplied by the vehicle manufacturer for the particular vehicle) is on a placard on the front door jam and is usually quite a bit lower than the Maximum pressure.

The carrying capacity of a tire increases with both size and pressure.
The traction increases with the contact patch area (which increases with lower pressure).

To sum up, if you have put on larger tires, you can air down to increase traction and also improve the ride quality since the tire asks as a spring and still have the same weight carrying ability as the stock size tires.

An example of this in the real world is 4WD Club runs where the maximum pressure allowed is 18 Psi to reduce trail damage due to tire slippage. Most of these vehicles have larger tires.

Off road race vehicles run around 35 Psi as a compromise between traction and rim cuts from hitting rocks, etc. at speed which push the tread up to the rim when too low a pressure is used.

Old (very old) race engineer)

References for those who are interested:
Circle Track Magazine
Race Car Engineering Magazine

and a few of several dozen books on automobile/racing design in one of my bookshelves:

CIMG0047 [800x600].JPG - 34kB

Cyanide41 - 11-30-2009 at 07:33 AM

Neal. Wouldn't 32psi be awfully LOW for a Max Psi?

Baja&Back - 11-30-2009 at 08:27 AM

I think ALL OF YOUSE should get into your rigs and go test out these statements in BAJA, right now!!
C'mon now ... :biggrin:

Barry A. - 11-30-2009 at 09:03 AM

Quote:

Originally posted by Cyanide41
Neal. Wouldn't 32psi be awfully LOW for a Max Psi?

Struck me the same way.

Barry

David K - 11-30-2009 at 10:16 AM

My last set of tires were Toyos, now I am on a set of Cooper Discoverer ATRs... 265/70-16... nearly identical to the Toyos.

Max pressure listed on the sidewall: 44 PSI. Recommended pressure for my '05 4 door Tacoma listed in the door jam: 29 PSI front/ 32 PSI rear.

Baja12valve - 11-30-2009 at 10:49 AM

I am always skeptical of "recommended" tire pressures from the factory. They are nothing more than a basic guideline. Different tires have different sidewall structures and stiffness, it is not a "one size fits all" deal. I also find that the factory pressures tend to be low for ride comfort. My Maximum pressure is 65 psi, cold. I run them front and rear at 60, not for comfort, but the wear pattern dictates that that is the correct pressure. Anything lower I get cupping and excessive wear on the shoulder, more, I get excessive wear in the center. I started at 45, the "recommended " pressure.

bajalou - 11-30-2009 at 11:19 AM

Just checked a couple of tires on my vehicles -

235-75-R15 Max. load 2025 at 35psi. Max pressure 35. Veh. recom. 35psi. Bronco II

31-1050-R15 Max load 2250 at 50 psi. Max pressure 50. Veh. Recom. 35 psi. Bronco

33-1250-R17 Max load 2025 at 35 psi. Max pressure 35. On desert rail so no veh recom. Tire is a off road tire. (Interco TrXus M/T).

235-85-R16 Max load 3415 at 80psi. Max. pressure 80. F350. Veh. Recom. 51 Front 80 Rear (BFG)

bajabass - 11-30-2009 at 01:32 PM

Aired down, 2wd will get you almost anywhere. If you get stuck, then hit the magic button! My Tundras, 3 in 7 years, state that in wet/slippery conditions, you can use 4wd hi, up to 65mph. The feeling of control is simply great. If the rear slips, the front pulls. If the front slips, the rear pushes. Off road, I use 2wd till I get stuck, then use 4wd to get out and turn around. Aired down and "skimming" washboard fire roads is a blast! 4wd hi has given me the best results. I am still running the crappy BFG Rugged Trail T/A's that came O.E. The 275/65/18 Dueller A/T Revos have to wait until I can burn up these originals. The door sticker says 30psi F, 33psi R. Tires are rated 44psi max. I run 40 psi front and rear and for a crappy tire, they work so-so.

Barry A. - 11-30-2009 at 02:05 PM

------I have destroyed 2 of those stock BFG Rugged Trails (only B rated), one a stick thru the sidewall, and the other a sharp rock thru the side wall, in the last 6 months on my X-Terra. I gave up on them and I have gone to E rated BFG All Terrain TA KO's (the only one's available from BFG for my size 265 x 75R 16's)----------we will see how they work. I carry about 35 to 40 lbs in them on the highway, and the ride is fine, and no noise. 25 lbs off road.

(tech info: Neal John's) :spingrin:

Barry

DanO - 11-30-2009 at 03:03 PM

Quote:

Originally posted by David K
Barry, you got there and back home the way you did, just fine... no worries!

With the newer shift-on-the-fly 4WD we have, it is easy to be driving 40-50 mph on a sandy, washboard road and click it into 4WD from 2WD and notice the difference in handeling, right away. You get a superior feel of control over your truck when it is in 4WD... less drifting or sliding.

I agree. This theory has been tested as late as yesterday afternoon from 1:15 to 2:00 p.m., as my wife drove the dirt from La Bocana de Santo Tomas to the highway. Immediately after I reached over to switch the F150 Supercrew into 4WH (ignoring the dirty look I got for interfering with her command of the vehicle), there was less lateral sliding on washboard, rocks and corners, and I was able to loosen my deathgrip on the passenger-side grab bar.

Barry, sorry to pile on. :yes:

Barry A. - 11-30-2009 at 03:20 PM

----you guys are all driving space machines, or hover craft-----you can't fool me!!!

Barry

woody with a view - 11-30-2009 at 06:06 PM

the tundra asks for 26 psi front. WAY TOO LOW! i dont like the way the sidewall bulges on hiway at 32-35psi so i put in a little more.

YMMV!!!

Barry A. - 11-30-2009 at 11:27 PM

Woody---------we ran our dozens of Ranger Rigs (lightly loaded 4x4 full size pickups, mostly) in the CA desert (El Centro area) with tire pressure at 26 lbs, both on road and off. We found over the years that pressure to be the best for flotation AND durability and longevity. We ran load range C tires, 10:00 x 15's on 8 x 15 inch. wheels.

Barry

bajabass - 12-1-2009 at 04:26 PM

Barry, I agree that the 26psi may work well under those conditions. Just don't try tossing a full size truck into a diminishing radius turn that soft. The tires will fold under in a heartbeat, or less. I guess I could slow down, NOT!!

David K - 12-1-2009 at 05:00 PM

Reducing pressure for sand driving is primarily needed on coarse arroyo sand or San Felipe/ Sea of Cortez beaches that have coarse sand and sea shell bits mixed in and without major deflating, even 4WD will get stuck... or really tear up the road/ beach... The idea is floatation and with your tires bulging like balloons, you will float over the sand and sink less than a human foot print!

The Tacoma with stock tires can cross deep sand at 20 psi, but does much better at 15 psi. If it gets 'stuck', then 10 psi always gets it unstuck (clear away built up sand from infront of the tires, differential/ skid plates... which would act like a parking break, otherwise!

Pump back up once off the beach or out of the arroyo.

alafrontera - 12-3-2009 at 04:24 PM

Thanks all, .... I think :?:

And They're All Going to A c-ckfight Tonight

Bajahowodd - 12-3-2009 at 04:56 PM

Quote:

Originally posted by alafrontera
Thanks all, .... I think :?:

I truly understand. Sometimes this forum has information overload. But, it's all good.

BajaWarrior - 12-3-2009 at 10:10 PM

My wife drives an '06 Honda CRV which has an emblem on it that says "All Wheel Drive" but no levers or switches inside to activate it.

Anyone one had one out on the beach yet? The tires seem pretty small for airing down.

TMW - 12-4-2009 at 08:40 AM

Quote:

Originally posted by BajaWarrior
My wife drives an '06 Honda CRV which has an emblem on it that says "All Wheel Drive" but no levers or switches inside to activate it.

Anyone one had one out on the beach yet? The tires seem pretty small for airing down.

When you air them down it's called rim-drive. Might work.

David K - 12-4-2009 at 09:08 AM

Quote:

It doesn't need activating, as it is always in ALL WHEEL DRIVE (I hope)... It will sense which tire(s) need power and apply... Check with the owner's manual for details.

Subaru Outback and Forester are ALL WHEEL DRIVE, as well. They drive the sand just fine. Air pressure down to 10 PSI possibly... My Subarus had 13" tires and did great at 10 PSI... all over the area!

1978 photo, Shell Island

[Edited on 12-4-2009 by David K]

VERY disappointing

alafrontera - 2-17-2010 at 06:02 PM

Well I decided to take the AWD Chevy Astro figuring it would be more comfortable for four people plus we could lock everything up. I guess that depends on how you measure comfort, do you mean while riding or while digging and pushing ? :rolleyes:

All I did was pull to the side of the road near the marina (San Felipe), not far at all. We sank in sand and just like any normal vehicle the left rear wheel was the only one spinning. How is this All Wheel Drive ???????

Before I decide to give up on the van and use the 4WD Ram 1500 next time I'm going to start a thread on tire deflation. :cool:

comitan - 2-17-2010 at 06:35 PM

Your Astro has problems, Mine will keep moving till I'm high centered and that is deep soft sand. Check your transfer case make sure it has fluid(The Purple stuff) fill it if not full, then take it somewhere and do donuts.

TMW - 2-18-2010 at 08:30 AM

Quote:

Originally posted by alafrontera
Well I decided to take the AWD Chevy Astro figuring it would be more comfortable for four people plus we could lock everything up. I guess that depends on how you measure comfort, do you mean while riding or while digging and pushing ? :rolleyes:

I'm not familiar with he AWD Astro van but my guess is that it controls the wheels thru a clutch and breaking system in the transfer case and or the brakes themself. Probably great for snow and ice but not so good in the sand.

David K - 2-18-2010 at 09:09 AM

Quote:

After all that everyone said here to you... did you deflate the tires??? 10 psi would have done the trick.

As for AWD...

It means all wheels with equal traction can get equal power, but usually means power will go to the tire that needs it most, of the four. In sand, with all four in a low traction situation, the power just went to one tire, all things being equal, it didn't matter which one.

Until I drove my new 2010 Tacoma with Traction Control limited slip, I would have to deflate my tires to under 20 psi (15 usually) for my Tacoma to drive on the San Felipe side sand... So, your getting stuck in an AWD or 4WD is NORMAL if the tires were at full pressure.

Air pressure is everything, power is not important.

Mexican fishermen drive their 2WD cars and trucks on that beach with deflated tires... Just park pointing downhill (it is a steep beach) to make getting started easy.

The new Tacoma was the first 4WD that drove with ease, without deflating... thanks to the limited slip traction system.

[Edited on 2-18-2010 by David K]

David K - 2-18-2010 at 09:20 AM

Oh, the initial question... AWD vs. 4WD:

AWD has a third differential instead of a transfer case to allow slippage between the front and rear axles for dry pavememnt driving, and there is no low range gearing.

4WD can be full time with a third differential or part time with a transfer case, but usually both offer a low range for steep crawling or torque in deep mud/ snow.

4WD is usually for SUVs, Trucks, Off road rigs.

AWD is usually for sports cars for cornering performance or family vehicles for security during snow storms.

Open differentials means power goes to the tire with least traction, for cornering ease (one front and one rear).

Limited Slip differentials means power will be transfered to the tire(s) with traction in a controlled manner and away from tires that spin freely.

Locking differentials means power goes to both tires on the same axle, equally. Turning may be difficult, so lockers should only be used to get unstuck or to move on to a better traction location.

Barry A. - 2-18-2010 at 09:58 AM

David------good stuff, as usual.

I have never been clear on all these type drive-systems, and now I am.

Thank you. I made a copy of this for my files so I will NEVER forget again. :spingrin:

Barry

David K - 2-18-2010 at 10:19 AM

Quote:

Originally posted by Barry A.
David------good stuff, as usual.

I have never been clear on all these type drive-systems, and now I am.

Thank you. I made a copy of this for my files so I will NEVER forget again. :spingrin:

Barry

It gets better, Barry... So technical that it scares most! LOL

I post now over on Tacoma World... really just trying to learn about the many options for traction control we new Toyota people have!

Here is a reply I had to someone asking for scenarios for using them... the nine drive modes we have.

=====================================================

Here is another way that may help to see the nine modes as being different:

Basically, we have:
1) 2WD with 'mild' LSD (Limited Slip Differntial called 'TRAC'),
2) 2WD with 'strong' LSD called "AUTO LSD", in the TRAC Off mode), and
3) 2WD with open differentials (VSC Off mode, for both TRAC and VSC off).

We have:
4) H4 with 'medium' LSD (TRAC with no engine output regulation), and
5) H4 with open differentials (VSC Off mode)

We have:
6) L4 with open differentials,
7) L4 with 'strong' LSD (A-TRAC)
8) L4 with rear locker and open front differential, and
9) L4 with rear locker and strong front LSD (A-TRAC).

As for when you use those 9 modes... well, whenever you need to! Seriously, the standard setting in H2 and H4 will work. I have never needed AUTO LSD because I have 4WD, so why put your truck through any stress?

H4 with TRAC is fantastic for most 4WD applications... I was amazed on how it took me over deep beach and arroyo sand without deflating the tires (as always necessary before).

L4... well this is the one mode that I say to push a button for, the A-TRAC button, and leave it that way. L4 is for slow crawling up and down grades or through deep snow/ mud... or if you do get stuck in sand. Amazing technology makes our Tacomas tractors (almost)!

Locking rear differential: Well, with A-TRAC I just don't know if this is important anymore. Better to have it and not need it, then to need it and not have it! Before A-TRAC, I used the locker many times for steep hill climbing... and it worked. Try a steep climb and if you are halted before you get to the top... try the locker and see if you get any further. My testing at Ocotillo Wells, didn't do anything more than wher A-TRAC got me... There is more 'testing' to do, however!

OPEN DIFFERENTALS? We have the option of making the differntial(s) open in all three drives (H2, H4, L4)... if you just gotta play in the snow or mud with one tire per drive axle spinning away, and the other doing nothing... like on the pre-2009 Tacomas.

So, you have traction opens galore! However, the standard mode in H2 and H4 will take care of you... and push the A-TRAC button once in L4 and leave it that way... making it the 'normal' mode in L4, will be the way to go IMO!

Have Fun Everyone!
__________________
2010 TRD OFF-ROAD 4WD DC with 9 drive modes (using VSC Off, A-TRAC & RR Diff Lock switches):

1) 2WD: VSC and TRAC active, 'Vehicle Stability Contro'l and 'Traction Control' (Limited Slip Diff.).
2) 2WD: Switch turns off 'TRAC' and 'VSC', and turns on 'AUTO LSD'. Gives maximum power to tire with traction by braking spinning tire, without cutting power.
3) 2WD: 3 second push of switch turns off VSC, TRAC & AUTO LSD for open differential.

4) 4WD-Hi: VSC and TRAC are both on. No engine power is cut in TRAC while in H4.
5) 4WD-Hi: 3 second push of switch turns off VSC and TRAC.

6) 4WD-Lo: VSC and TRAC are off (open differentials).
7) 4WD-Lo: Push of A-TRAC button activates A-TRAC (Locker-like limited slip).
8) 4WD-Lo: Push of RR DIFF LOCK switch to lock rear differential.
9) 4WD-Lo: RR DIFF LOCK and A-TRAC combined. 5 MPH limit.

David K - 2-18-2010 at 10:23 AM

From the Internet

--------------------------------------------------------------------------------
Another... from: http://behindthewheelnews.toyota.com/

Over the past several years, driver assistance features have become commonplace. The functionality and convenience of these systems continue to help develop vehicle collision avoidance capabilities. By their very nature, driver assistance systems are designed to help detect, judge and react to anticipated collision scenarios.

Anti-lock braking system (ABS) is probably the best known driver assistance feature. ABS has evolved from simple lockup control only during braking to more advanced systems that control traction during acceleration, braking and cornering by braking wheels individually while integrating other vehicle operating factors such as engine power output.

Most new vehicles are equipped with ABS these days, but ABS is not a one-size-fits-all system. ABS can include a number of additional features, which are found on a number of Toyota vehicles:

•Electronic Brake-force Distribution (EBD) -- modifies braking force at individual wheels to compensate both for changes in vehicle load (occupants and cargo) and to help increase braking efficiency during cornering.

•Brake Assist (BA)1 -- monitors the force with which the driver depresses the brake pedal and provides additional brake fluid pressure when the system detects an emergency stop.

•Traction Control (TRAC) -- helps reduce drive wheel spin during acceleration using ABS and control of engine power output.

•Vehicle Stability Control (VSC)2 -- helps prevent skidding or spinning while cornering by controlling ABS and engine power output to help keep the vehicle traveling in the steered direction, even if the driver enters a turn too fast or steers the vehicle too sharply for road conditions.

•Vehicle Dynamics Integration Management (VDIM)2 -- combines a range of vehicle stability control functions into a single, seamless process to help provide overall vehicle dynamic drivability.

SUVs and trucks, such as the Toyota Tundra and 4Runner, may be equipped with specialized ABS-based functions such as:

•Active TRAC (A-TRAC) -- During 4-wheel-drive operation on a snow-covered road or in rugged off-road conditions, A-TRAC controls engine output and brake fluid pressure so that the drive force is distributed to the wheels that have traction. This enhances drivability in extreme road conditions, an effect that is similar to a Limited Slip Differential (LSD). Off-road drivability is equivalent to having the center differential locked and a Limited Slip Differential on both front and rear axles.

•Auto Limited Slip Differential (Auto LSD) -- Auto LSD uses the TRAC system to achieve the capability of a Limited Slip Differential (LSD) when driving in 2WD mode. (On a 4WD vehicle, Auto LSD only operates when the vehicle is being driven in 2WD mode.) Because Auto LSD and Rear Differential Lock perform similar functions, vehicles may have one system or the other, but not both. While Auto LSD components are similar to those in the TRAC system, there are important differences.

•Downhill Assist Control (DAC)3 -- DAC allows the vehicle to descend a steep hill in a stable manner without the wheels locking. It does this by controlling hydraulic brake pressure at all four wheels, helping to maintain a constant, low vehicle speed.

•Hill-start Assist Control (HAC)3 -- The basic function of the HAC system is to help increase control on steep upgrades and stopping and starting on slippery surfaces. The HAC system is designed to help prevent the vehicle from rolling backward or slipping sideways during transition from a stopped position to climbing an upgrade.

David K - 2-18-2010 at 10:27 AM

This from: http://www.sae.org/technical/papers/2000-01-1636

Active-TRAC (A-TRAC) is the system for off-road 4WD vehicles. This system consists of independent four wheel brake control system and engine torque control system.

This system applies the brake to any spinning wheel, and sends torque to the other wheels with grip. Therefore, the vehicle gets strong LSD(Limited Slip Differential) effect, and it has the same traction performance as a center and rear differential locked vehicle.

Because the vehicle with A- TRAC does not have a differential locking mechanism, it no longer has the phenomenon of tight corner braking, and it frees a driver from operating the differential locking system. Therefore anyone can easily enjoy off-road driving with A-TRAC.