ATRAC question.

S

ScottAW

New member
Was reading some older thread and saw someone post that the feature "ATRAC" acted like a limited slip for both the front and rear axles. Do both the v6 and v8 4-Runners have this feature?

One of the reasons I'd prefer the v8 to the v6 is the AWD feature, as I don't really want a RWD w/out a limited slip. But if the ATRAC acts as a limited slip in 2wd mode, then the v6 4-runner doesn't sound so bad now. :)

2 months on my current lease... then it'll be time to pick out my 4-Runner. :D
 
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TRAC

The 4WD, both V6 and V8, have 4 wheel traction control. I am not certain about the 2WD vehicles or the 4WD V6 when it is in 2WD mode, there may be something similar in this case for the 2 drive wheels.

In 4WD the traction control (as I remember it is called just TRAC, not ATRAC) will apply braking to a wheel that is slipping so that the open differential can send torque to the non-slipping wheel; this compensates for not having limited slip or locking front and rear differentials. The center differential is a limited slip (Torsen) and can also be locked (and locking the center differential also turns off VSC).

I actually would have liked to be able to select between 2WD and 4WD as with the V6 models but wanted the V8 more.

I had a chance last weekend to take my 4Runner off-road in the Anza-Borrego desert. There were sections of trail where the sand was soft and deep enough that it was difficult to walk but the truck with a locked center diff. and in 4Lo did just fine. I took a wrong turn on one trail and cut across a section of really soft and deep looking sand to get back on course, my navigator thought that we were going to get stuck for certain ("Oh no, were dead!" were his words) but I just kept the truck moving at a constant speed and didn't get stuck.

PS
You could get a 4WD V6 and always leave it in 4WD mode just as if it were a V8 model. But, I really love the power (and sound) of the V8 (the gas mileage does suck though).
 
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I think the ATRAC feature will electronically "nanny" you to a standstill. It really hates wheelspin and is super aggressive at stopping it by clamping the brake on the offending wheel, and de-throttling the engine if neccessary as well.
I found several steep hills in the area I live impossible to climb when they were snowed up with the truck in 2WD mode . The truck was slowly brought to a standstil, ATRAC yammering away, complaining of my attempt, "No wheelspin allowed son, sorry!!".
But when in 4HI, no problems, plenty of traction when the power is distributed to 4 wheels. I could still get the "nanny" to go off by trying to accelerate, but the truck does remain very stable and straight.
With the center differential locked however, it's a different story. VSC is off with the center diff locked, and I was able to spin the wheels up the hills, and the truck was MUCH more liable to start a sideways slide, and I had to back off the gas.
I am actually pleased with the VSC, I think I would be smoking the rear wheels while making low spped turns, if it weren't for the "nanny".
 
Thanks for the info. guys.

Makes sense though. When I test drove the V6 I goosed the throttle to see if the rear end would break traction while bolting across a somewhat bumpy intersection. I heard/felt the wheel slip momentarily but then it zipped right across the intersection. It felt like it had a limited slip, but was very smooth in transitioning the power to the left rear wheel. (the right rear wheel broke traction momentarily) This was in 2WD mode for the v6 4x4.
 
(A)TRAC vs VSC

I think the ATRAC feature will electronically "nanny" you to a standstill. It really hates wheelspin and is super aggressive at stopping it by clamping the brake on the offending wheel, and de-throttling the engine if neccessary as well.
Click to expand...

I think we are using the terms ATRAC and TRAC to mean the same thing but I believe that it is only VSC that will dethrottle the engine and, as you mention, locking the center differential will disable VSC.
 
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In 2wd 4runners (2wd only), the rear axle has traction control. It can also be turned OFF.

In 4wd 4runners, while in 2wd mode, traction control is active on the rear axle. It canNOT be turned off. With 4wd models, VSC is the ONLY thing that can be turned off (by locking center diff).

ATRAC is equally effective as any limited-slip differential. However, it is not as effective as a pure locker.

ATRAC actually does NOT transfer torque side to side as explained by Toyota brochure...it PREVENTS one wheel from losing total power. Let's look at one axle only.

If one wheel is on ice and the other is on dry land, then the wheel on ice will spin. The wheel on dry land will have no power. Why?? Well, power/torque flows to the wheel with the LEAST resistance...thus, it flows to the wheel on ice. Ok, so what does ATRAC do?? ATRAC uses ABS sensors and looks at the speed differences between the two wheels. Since the wheel on ice is spinning faster than the other wheel, ATRAC applies braking power to that wheel...slowing it down to the same speed as the other wheel (THAT is it's goal). By doing so, you are increasing resistance to the spinning wheel...thus, allowing engine power to now flow equally to the other wheel (since both wheels have equal resistance). Thus, in theory, the maximum power one wheel gets is 50%...never 100%. Thus, it prevents the wheel with traction (dry land) from losing power.

Hope this helps.
 
Im still working on a way to disable VSC... anytime I want...

the closest mod Im going to be researching (while I now have the manuals) is the same mod the LC's use... the center diff mod

allows you to lock your center diff in any mode... 2wd even...

hence hopefully if it works... no VSC in 2wd =D
 
Ducky said:
Im still working on a way to disable VSC... anytime I want...

the closest mod Im going to be researching (while I now have the manuals) is the same mod the LC's use... the center diff mod

allows you to lock your center diff in any mode... 2wd even...

hence hopefully if it works... no VSC in 2wd =D
Click to expand...

To disable VSC, just lock the center.

Btw, you can't lock the center diff in 2wd. Locking the center will transfer 50% to the front / 50% to the rear. You can only lock center in 4wd.....
 
Not sure but I suppose you can give it a try.

I know the Old LC's have 3 lockers (f/c/r) and I'm not sure exactly how their vsc is setup but I'm suspecting that their version of vsc only gets disabled when in 4lo?

I know my 4runner which I believe is the same as yours in a sense that once you lock the center, vsc will automatically be disabled. I think that mod you're looking at is making it possible to disable the vsc while in 4hi as well as the intended 4lo.

Just some food for though but don't quote me as I'm not sure exactly how that mod works for the LC (as I'm not familiar w/ their 4wd system).

GOod luck! Post some results too btw
 
Ok...for clarification:

1. VSC = stability control
2. ABS = anti-lock braking system
3. ABS was standard in the previous gen Land Cruiser (TLC 80)
4. VSC was NOT available on the TLC 80
5. VSC was ONLY available on the current gen Land Cruiser (TLC 100) starting in 2000...which means that not all TLC 100 have VSC.

So, the "mod" that you link to applies to disabling ABS on TLC 80. VSC uses ABS sensors to work, but it also takes info from many other units, such as steering unit, g-sensor, throttle sensor, etc.. Thus, the mod will likely screw up a lot of things if you use it on your 4runner!! DO NOT DO IT. The mod does NOT apply to any Toyota SUVs after 2000.
 
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