4th Gen Stuck In The Sand

L

lmlenzen

New member
So I have to say I am disappointed... From everything I have read it seems like the 4th Gen 4Runner has an excellent Torsen center diff which can be locked. But what about the front and rear diffs? I figured the VSC & TRAC would handle the wheel spin from left to right. Granted the driver here is not that great and doesn't use the brakes or limit his throttle but I still expected the 4Runner to transfer some power to the 2 wheels that weren't spinning at all. Anyone know what went wrong here?

Toyota 4th Gen information... (Page 28)
http://www.toyota120.com/GenDocs/2003_4Runner.pdf

First video...
http://www.youtube.com/watch?v=umLO_vbtDPM

He eventually gets out...
http://www.youtube.com/watch?v=l_WqlZKP2kU&feature=related
 
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I would chalk that up to 2 things...

1) The driver did not air down his tires before entering the sand and thus dug into the sand instead of floating on top.

2) the driver continued to dig himself deeper into the sand by spinning his wheels instead of getting out and digging himself out or getting something to gain traction on.

The diff lock does not lock side to side, but instead gives 50% power to front and 50% power to rear, and allows you to spin the wheels instead of the system using braking to slow the spinning wheels to give the others traction. Honestly, if he had left the center diff lock off, he might have actually freed himself, but based on the depth of the ruts, I think he needed to dig himself out first or put something behind a wheel to gain some traction - like the individual you see behind it in the second video.
 
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ha, mustve done something dumb.

ill bet he came in slow, in 2wd, the front wheels sunk and dug, and by then it was too late.

ive never been EVEN close to stuck in sand (stock or no)...... so i cant really see an explanation.
 
lmlenzen said:
So I have to say I am disappointed... From everything I have read it seems like the 4th Gen 4Runner has an excellent Torsen center diff which can be locked. But what about the front and rear diffs? I figured the VSC & TRAC would handle the wheel spin from left to right. Granted the driver here is not that great and doesn't use the brakes or limit his throttle but I still expected the 4Runner to transfer some power to the 2 wheels that weren't spinning at all. Anyone know what went wrong here?
Click to expand...

I saw no evidence, mechanical or behavioral, that would convince me the center diff was locked.

At the beginning of the 1st video we see the front passenger tire roosting like crazy while the rear passenger tire is static but no sand being thrown from the rear driver's side. Also, the inexperience shown in the extraction attempts would seem to fit with a failure to lock the diff.

I've cruised all around Pismo (granted, at 12 psi) in the deepest sand, going up and down hills for many hours, never getting stuck.
 
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What would be the ideal way to get out of a situation like that, if you were too lazy or forgetful to air down your tires, or possibly it was just a turn-off from the road that caught you off guard. Lock the diff and put it into 4-Lo?
 
Poor driving

I no doubt agree that he is a poor driver as I stated in the initial description. My question relates to why didn't the traction control transfer some power to the 2 wheels with traction?

I have also taken my 4Runner off road a lot and never gotten stuck but placed in this exact position I'm just surprised at no transfer left to right or right to left. I would definitely have dropped her into 4Lo and used braking to get myself out but after reading all of the traction control information on the 4th gen I thought it would do it automatically.
 
I think his diff was locked because of the wheel spin. VSC/TRAC would prevent wheel spin.

If you were to find yourself in that situation, I would get out and air down the tires... Instead of digging deeper, put as wide of a footprint on the sand as possible. Clear out as much sand from in front of or behind the tires and then go slow, don't floor the accelerator trying to get out. If you still don't gain traction, find something like a board (I have used floor mats) to gain traction that will increase the footprint even further on the sand.

The keys to driving on sand are similar to driving on snow. No sudden stops or starts, no sharp turns and keep the speeds reasonable. You won't slip on sand, but you can easily dig in and if you continue.
 
Is VSC/TRAC turned off when the diff is locked? If the diff had been unlocked would the VSC/TRAC transfer power correctly?
 
I think you dug a hole and looked like you front end was hung up.

Tire pressure and what type of tires .

Even with locking the center diff. which splits front and rear and disable VSC/TRAC , ATRAC should be enabled getting all 4 wheels to spin . I do think ATRAC does cut out at a certain RPM , not sure though.

I have no problems getting all 4 wheels to spin / drive with Atrac. I just did that in one of our storms going up a rutted snow cover hill , went relatively slow and let it do its thing , then played with the gas and was throwing up snow from all 4 wheel spinning , I could see it , so could my spotter.
 
lmlenzen said:
Is VSC/TRAC turned off when the diff is locked? If the diff had been unlocked would the VSC/TRAC transfer power correctly?
Click to expand...

Yes. If you lock the diff, you will see the VSC/TRAC Off light up on the dash and you can spin the wheels.

If the diff had been unlocked, the VSC/TRAC would have attempted to brake the spinning wheel to give traction to the wheel that was not spinning.
 
Now I think I am more confused.

Falls you are saying that with the diff unlocked it would cut power to all wheels and get nowhere? But if it was locked then ATRAC would pull it out but only at a certain RPM? If the driver hadn't given so much gas and had it in 4Lo do you think ATRAC would have transfered the power properly?
 
Not one of you guys gave a good explanation why he was getting the right front and left rear tires spinning without any movement at all from the other two tires.

To me, this seems like exactly what one would expect to see happen on a 4wd vehicle with open differentials. Now of course we all know that the 4Runner has open diffs front and rear, but that's the exact reason for ATRAC. It is supposed to brake the spinning wheel on one side to provide power to the wheel on the other side. I didn't see that happen at all in the video. Instead, the 4Runner in the video seemed like it had two open diffs and no ATRAC at all. Very strange.

Locking the center differential does not disable ATRAC, so it should have helped whether the driver had it locked or not. My own 4Runner has never had the problem shown in the video with opposite tires front and rear spinning freely and the other two tires dead like that.
 
lmlenzen said:
Now I think I am more confused.

Falls you are saying that with the diff unlocked it would cut power to all wheels and get nowhere? But if it was locked then ATRAC would pull it out but only at a certain RPM? If the driver hadn't given so much gas and had it in 4Lo do you think ATRAC would have transfered the power properly?
Click to expand...

VSC, is skid control which cuts power. VSC is disabled when the center diff is locked. 2008 models have a VSC off button, so the center diff doesn't need to be locked. I think if he had the front wheels straight, VSC might not have cut power.

In Thai's post, ATRAC is most effective at 1500RPM or so. I was on a sloped driveway that was iced over. The 4Runner wouldn't budge, I could see the wheels on my side slip and spin. But got the engine over 1500RPM it started to move up the driveway. I was in 4H and diff unlocked.

Haven't gotten the 4Runner in sand yet.
 
lmlenzen said:
Now I think I am more confused.

Falls you are saying that with the diff unlocked it would cut power to all wheels and get nowhere? But if it was locked then ATRAC would pull it out but only at a certain RPM? If the driver hadn't given so much gas and had it in 4Lo do you think ATRAC would have transfered the power properly?
Click to expand...

Atrac is always on , no matter if your diff. is locked or not . If the diff. is unlocked an senses any significant wheel spin (VSC/TRAC) cuts off power to the wheels.

At what RPM does the ATRAC get overide , I do not know , I thought it was more like 2500-3000 rpm , but thats just what I read on here.

I really have no clue why the truck was performing like that and Atrac not engaging.

I do know that loose sand like that , literally can be like quicksand for any vehicle , it's an easy stuck for most vehicles if you dont drive correctly , have proper tires that are aired down.
 
I think something may have been wrong with that 4Runner. There's no way it should have acted like that in the video.
 
A few quick notes on what I saw:

- Center diff was probably locked, although there is no way to tell this for sure from looking at video.
- I see both front passenger tire AND rear driver's tire spinning...and there was a big rooster tail, so this leads me to believe that center diff was locked.
- Again, center diff lock = VSC OFF. ATRAC/TRAC is still ON in all modes. 4x4 system on 4runner: http://www.toyota-4runner.org/showthread.php?threadid=12
- VSC is the main culprit in dethrottling the engine power.
- Does ATRAC/TRAC dethrottle you? Yes, it does, but not nearly as much if VSC was ON.
- ATRAC/TRAC does bog you down if you're gentle on the throttle...remember, it BRAKES your spinning wheel, so momentum can be lost if you are gingerly with the throttle.
- ATRAC/TRAC, by definition, PREVENTS rooster tail from happening. VSC does this also by different computer logic.
- What i found on my 2002 4runner with ATRAC/TRAC is that if i were to push on the gas pedal and get RPMs above 2500-3000, ATRAC/TRAC would intervene less, allowing me rooster tail my tires. And this is what this driver did in the video i believe.
- The rooster tail on the front side tells me that the throttle was not the problem here.
- The reason why you do not see rooster tail on the driver's side rear tire is because it was barely touching the sand...in other words, the 4runner rear axle maxed out it's articulation. Notice that when the fat guy jumped on the rear bumper, you can THEN see the rooster tail from the driver's rear tire.

What does this all mean? Well, remember, ATRAC/TRAC has it's limitations. In a Hummer H2 brochure, ATRAC can transfer enough power to one wheel to get H2 up an incline of ONLY 10 degrees max. Normally, H2 can go up much steeper incline if all wheels have traction.

How ATRAC works: http://www.toyota-4runner.org/showthread.php?s=&threadid=5036

This guy's problem was that he was bog down pretty deep in sand. That is, he seemingly sunk down to near frame height...which means there is A LOT of resistance going forward from bumpers, skidplates, crossmembers, etc.

In all likelihood, ATRAC/TRAC tried it's best to transfer torque to the wheels with traction (driver's front, passenger rear tires), but due to the load it has to go against (aka resistance discussed above), there was simply not enough power to get it moving forward. Remember the H2 example above...ATRAC can only do so much against a load whether it be sand, mud, or inclines. ATRAC can only transfer a fraction of engine power to the wheel(s) with traction.

Notice how this guy got out. He got out by reversing himself. If he concentrated on this initially, then he would have gotten out faster in my opinion. There was less resistance if he backed up. (His front nose was touching the sand...too much resistance in going forward.) Less resistance = easier for ATRAC transfer of torque to wheel(s) with traction to work.

ATRAC is pretty hard to break since it uses existing ABS software and hardware. However, it is possible that ATRAC/TRAC went into "limp home mode" IF this guy (in video) has been off-roading a whole lot and abusing the ATRAC/TRAC. ATRAC/TRAC shuts down if you use it continuously for a long time to prevent overheating your brakes and related systems. According to Toyota, the new Land Cruiser with Crawl Control (ATRAC/TRAC cruiser control) can run it's ATRAC/TRAC system continuously for only 12 minutes before shutting down. And according to Toyota, this is pretty long for such a system. I would assume that this also applies to the 4runner's system. Do i believe that this is what happened? No, because the guy got out by reversing himself, which means that ATRAC/TRAC was still active to do so. He only had traction on two tires (one front and one rear)...so, he MUST have an active system to get out...otherwise, a vehicle without any ATRAC/TRAC would not be able to.

What are the basics in sand:
- Air down
- Don't lose momentum or you're screwed (like videos above)
- Go off-roading with a 2nd vehicle to tow you out or vice versa

Hope this helps.
 
Thai, thanks for the excellent detailed description. I didn't realize that ATRAC had such low limitations but from an engineering standpoint it does make sense.

Think 5th gen 4Runners will have at least a LSD in the front and rear?
 
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