4th Gen guide on VSC, TRAK, ATRAK Diff lock, etc?

[matphat]

Hello all,

Been wheeling my 2008 v8 for about 5 years now and I still don't feel like I have it all figured out. I do all my wheeling solo and have never had anyone to show me the ropes.

What I'm looking for is a guide that spells out the 4th gen's worky bits and when/how to use them.

All I do when I go wheeling is air down, throw it in 4Lo, lock the center diff and take off. Must be a bit more to it, right?

 

[Quorth]

VSC applies the breaks to help maintain traction when it senses the car is sideways/sliding.
TRAC cuts power to help maintain traction
ATRAK uses the breaks to help get traction at low rpm's
Center diff lock - locks 50/50 power to both axles

So with the '08 you should have a button on the left by the center diff lock thats for traction control. Single press should turn off vsc, press and hold should turn off vsc and trac. No current way to turn off ATRAK without doing a mod.

In the v8 locking the center diff also turns off VSC.

You should turn off VSC/TRAC if you're trying to spin your wheels (whatever the occasion)

 

[AspenBob]

Here is another way to understand what is going on:
VSC:
PURPOSE: Helps correct skids while cornering too fast at highway speeds.
HOW DETECTED: Steering angle doesn't match direction vehicle is going.
INTERVENTION: Reduces engine power, brakes one or two wheels.
PROBLEMS: Can cut power just when you need it! In deep snow, sand, or mud, turn it off.
ABS:
PURPOSE: Avoid skid while braking.
HOW DETECTED: While braking, one wheel is turning slower than the others.
INTERVENTION: Reduces braking on that wheel.
COMMENTS: A lifesaver! In a panic stop, even on snow or ice,, you should stomp the brakes hard, and let the ABS control the stop.
ATRAC:
PURPOSE: Prevent wheels spin while accelerating, especially in low range.
INTERVENTION: Applies brake to the wheel that is spinning.
PROBLEMS: Can get confused. Works best in low gear, low range. Keep a slow steady rpm.
COMMENTS: Works great! For most wheelers it is as good or better than lockers, as it it is always available, doesn't bind the steering, etc.
CENTER TORSEN DIFF:
PURPOSE: Allows 4wd to be used on dry pavement without binding, wheel scuffing, or breakage. Sends more torque to the axle that has traction.
INTERVENTION: Differential effect allows turns without binding. Torque sensing distributes torque where needed. Can be locked if needed.
COMMENTS: All 4wd vehicles should have this! All 4th gens have this, but not the more recent models. (All Limited Editions have it) Use 4wd whenever and wherever. Less wheelspin. If I ever buy a new 4runner, I'll get a Limited just to have this feature!
LOCKING THE CENTER DIFF: Rarely needed. IMHO, only needed if you need extra traction to start from stopped. Also needed to back down from a failed steep hill climb. Otherwise, let the torque sensing distribute the torque.

 

[WyEast-08]

I get really confused on this, because I guess Ive seen several different explanations for the 2008 V8 limited. I had thought from reading other posts here that pushing and holding the VSC-OFF button (next to the center diff switch) turned off both VSC and ATRAC off. And that putting it into low range would disable VSC and engage ATRAC. Can someone confirm how to engage ATRAC with the 2008 V8?

 

[Syr4RinNC]

I get really confused on this, because I guess Ive seen several different explanations for the 2008 V8 limited. I had thought from reading other posts here that pushing and holding the VSC-OFF button (next to the center diff switch) turned off both VSC and ATRAC off. And that putting it into low range would disable VSC and engage ATRAC. Can someone confirm how to engage ATRAC with the 2008 V8?

So theres different theories. unfortunately its tough to test without being off road

Some say ATRAC is always engaged will always work if you start spinning your wheels

Others say that if you engage 4lo it kicks in.

Overall for me, one of my gripes is that im not super impressed with the 4th gen off road traction control features. I feel that I have to use momentum more often than not as opposed to constant low speeds when climbing steep hills or off camber etc. My goal generally is slow steady speed so I dont break or damage things, but I definitely struggle with that approach and often need back up and give more gas, back up give it more gas repeat, repeat, repeat

 

[WyEast-08]

It sounds like I will need to try different options of using 4-lo, or VSC-off button until I get a better handle on it. I guess a good excuse to get outdoors this weekend!

 

[rdruss]

I have an '03 V8 Ltd so it is AWD. Does anyone know what happens when the center dif lock is engaged. I know it distributes torque to front/rear axles equally but how is it" locked"? What is actually happening? Why can it not still be driven on dry pavement making turns? (Or can it?)

I've watched the Weber Auto youtube presentation about Center dif transfer case, which is VERY informative as he uses a Tcase from an '04 Runner Ltd. but he doesn't get into the locking mode.

Please don't respond with " I think", I've already done that!

 

[Syr4RinNC]

So this probably isn't what youre looking - as there are more eloquent/ precise answers

when the center diff is locked - the transmission sends equal power and torque to both the front and rear differentials for the front and rear to generally spin at the same rate

When turning (when driving forward) the rear wheels (going relatively straight) are going to want to spin more than the front tires (going a smaller distance while turning). As a result there is risk that propeller shaft/ driveline can get wound up or "bind" and it can put additional stress on the differential and driveline components [i may have this backwards and I got myself all confused thinking about]. but also the rear wheels kinda cut the corner and travel a shorter distance than the front wheels when turning.

So you need some wheel slip when diff is locked to prevent that from happening or to make very gradual/ gentle turns

 

[rdruss]

So this probably isn't what youre looking - as there are more eloquent/ precise answers

when the center diff is locked - the transmission sends equal power and torque to both the front and rear differentials for the front and rear to generally spin at the same rate

When turning (when driving forward) the rear wheels (going relatively straight) are going to want to spin more than the front tires (going a smaller distance while turning). As a result there is risk that propeller shaft/ driveline can get wound up or "bind" and it can put additional stress on the differential and driveline components [i may have this backwards and I got myself all confused thinking about]. but also the rear wheels kinda cut the corner and travel a shorter distance than the front wheels when turning.

So you need some wheel slip when diff is locked to prevent that from happening or to make very gradual/ gentle turns

Thank you. I thought about it some more based on the Weber Auto video. He started out talking about the standard 4WD transfer case and the components involved. Then he went to the AWD Tcase ('04 4Runner) and explained that the center diff is necessary to allow the front and rear axles to respond like the right/left wheels of an open diff. Now I see that when the center diff is "locked" the Tcase reverts back to a standard 4WD arrangement because the center diff is basically "removed" because it is locked, it is no longer performing like a differential. I think I got it!

 

[AspenBob]

Sy4RinNC, you mentioned that you are not super impressed with the offroad traction control. Can you describe in a little more detail what is or isn't happening?
My good experiences with it have all been in low range . Whether VSC is on or off normally doesn't matter. I will be climbing a steep hill, going fairly slowly, perhaps 3 - 10 mph. A wheel will lose traction and start to spin. It will only spin about 1/2 turn, and the Atrac will catch it, by applying the brake to that wheel. It will make the same rat-a--tat-tat noise that ABS makes. After only the slightest hesitation, I move forward. During the process, I keep a steady pressure on the throttle.
Does this sound like what is happening to you?

 

[Syr4RinNC]

Sy4RinNC, you mentioned that you are not super impressed with the offroad traction control. Can you describe in a little more detail what is or isn't happening?
My good experiences with it have all been in low range . Whether VSC is on or off normally doesn't matter. I will be climbing a steep hill, going fairly slowly, perhaps 3 - 10 mph. A wheel will lose traction and start to spin. It will only spin about 1/2 turn, and the Atrac will catch it, by applying the brake to that wheel. It will make the same rat-a--tat-tat noise that ABS makes. After only the slightest hesitation, I move forward. During the process, I keep a steady pressure on the throttle.
Does this sound like what is happening to you?

Basically, I dont feel confident in my traction. I have decent tires (relatively new Falken Wildpeak At3) and find that when Im climbing on a hill/ MTN either in dirt/ over rocks, roots, sticks or on clay and rocks that I cant maintain a constant speed to continue to climb, climb, climb. (These are generally on moderate rated off road trails)

I hear the brakes engage and the grinding (The sound of ATRAC on a toyota is unmistakable)

I often get stuck in places I wouldnt expect (IE not necessarily thick mud or a large obstacle) and have to use a lot more momentum and speed when climbing than I would like.

Ideally id like to be able to go at 5 MPH give or take steadily up a hill and I just find that thats not the case. Id be curious how the 5th gens with crawl control/ multi terrain select compare - but I havent had access to one I can ding up on a trail yet

 

[LaZorChicKen]

Upgrading your ring and pinion will help with that. I upgraded mine to 4.88 and can crawl super slow without needing momentum.

 

[rcan1015]

Here is another way to understand what is going on:
VSC:
PURPOSE: Helps correct skids while cornering too fast at highway speeds.
HOW DETECTED: Steering angle doesn't match direction vehicle is going.
INTERVENTION: Reduces engine power, brakes one or two wheels.
PROBLEMS: Can cut power just when you need it! In deep snow, sand, or mud, turn it off.
ABS:
PURPOSE: Avoid skid while braking.
HOW DETECTED: While braking, one wheel is turning slower than the others.
INTERVENTION: Reduces braking on that wheel.
COMMENTS: A lifesaver! In a panic stop, even on snow or ice,, you should stomp the brakes hard, and let the ABS control the stop.
ATRAC:
PURPOSE: Prevent wheels spin while accelerating, especially in low range.
INTERVENTION: Applies brake to the wheel that is spinning.
PROBLEMS: Can get confused. Works best in low gear, low range. Keep a slow steady rpm.
COMMENTS: Works great! For most wheelers it is as good or better than lockers, as it it is always available, doesn't bind the steering, etc.
CENTER TORSEN DIFF:
PURPOSE: Allows 4wd to be used on dry pavement without binding, wheel scuffing, or breakage. Sends more torque to the axle that has traction.
INTERVENTION: Differential effect allows turns without binding. Torque sensing distributes torque where needed. Can be locked if needed.
COMMENTS: All 4wd vehicles should have this! All 4th gens have this, but not the more recent models. (All Limited Editions have it) Use 4wd whenever and wherever. Less wheelspin. If I ever buy a new 4runner, I'll get a Limited just to have this feature!
LOCKING THE CENTER DIFF: Rarely needed. IMHO, only needed if you need extra traction to start from stopped. Also needed to back down from a failed steep hill climb. Otherwise, let the torque sensing distribute the torque.

Just bought a 2008 T4R and your explanation was very helpful. Thx.