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DanO
Super Nomad
Posts: 1923
Registered: 8-26-2003
Location: Not far from the Pacific
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| 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.
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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. 
\"Without deviation from the norm, progress is not possible.\" -- Frank Zappa
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
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Mood: optimistic
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----you guys are all driving space machines, or hover craft-----you can't fool me!!! 
Barry
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woody with a view
PITA Nomad
Posts: 15939
Registered: 11-8-2004
Location: Looking at the Coronado Islands
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Mood: Everchangin'
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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!!!
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
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Mood: optimistic
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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
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bajabass
Super Nomad
Posts: 2016
Registered: 10-4-2006
Location: La Paz,BCS
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Mood: Want to fish!!!
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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!!
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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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.
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alafrontera
Nomad
Posts: 143
Registered: 11-4-2009
Location: San Diego
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Thanks all, .... I think 
low lattitude attitude
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Bajahowodd
Elite Nomad
Posts: 9274
Registered: 12-15-2008
Location: Disneyland Adjacent and anywhere in Baja
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And They're All Going to A c-ckfight Tonight
| Quote: | Originally posted by alafrontera
Thanks all, .... I think |
I truly understand. Sometimes this forum has information overload. But, it's all good.
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BajaWarrior
Super Nomad
Posts: 2307
Registered: 9-27-2006
Location: Mission Bay, San Diego. Playa Hermosa, San Felipe.
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Mood: Anxious to get south
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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.
Haven't had a bad trip yet....
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TMW
Select Nomad
Posts: 10659
Registered: 9-1-2003
Location: Bakersfield, CA
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| 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.
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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| 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. |
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]
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alafrontera
Nomad
Posts: 143
Registered: 11-4-2009
Location: San Diego
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VERY disappointing
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 ? 
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. 
low lattitude attitude
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comitan
Ultra Nomad
Posts: 4177
Registered: 3-27-2004
Location: La Paz
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Mood: mellow
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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.
Strive For The Ideal, But Deal With What\'s Real.
Every day is a new day, better than the day before.(from some song)
Lord, Keep your arm around my shoulder and your hand over my mouth.
“The sincere pursuit of truth requires you to entertain the possibility that everything you believe to be true may in fact be false”
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TMW
Select Nomad
Posts: 10659
Registered: 9-1-2003
Location: Bakersfield, CA
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| 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 ?
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. |
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.
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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| 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 ?
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. |
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]
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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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.
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
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Mood: optimistic
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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. 
Barry
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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| 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.
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.
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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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.
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David K
Honored Nomad
Posts: 64852
Registered: 8-30-2002
Location: San Diego County
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Mood: Have Baja Fever
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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.
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