I thought you couldn't turn off the A-TRAC (w/ the 4x4). I know the 4x2's have a switch to turn it off though.

 

What's the DAC? ...nevermind. I forgot, it's that downhill chauffeur thing.

Do you suppose maybe the 4th gen system is different from the 3rd gen and you can do burnouts with it? I haven't observed that I can with the 3rd gen. I definitely can't do donuts in sand like I could with a "regular" truck.

And in reponse to hillbilly's thoughts, usually when I want some wheel spin, I'm in the 2nd or 3rd low-range gear. I can't testify either way as to whether lo/lo allows spin. (Hard to spin when you're going so slow.)

You know, going onto a slightly different track with this conversation, I wonder if the reason VSC turns off when you lock the center diff is because that system's algorithm for doing corrections assumes the front and back drive shafts spin independently and makes corrections taking into account all four wheels, whereas ATRAC is more about simulating a limitted-slip on each axle? (I have less of an idea of exactly what VSC does than I do of ATRAC.)

 

Taken from another source:

Vehicle skid control --- or VSC--- helps to maintain cornering stability in situations where the vehicle is about to lose traction and skid sideways. VSC senses when too much steering input is applied while the vehicle is traveling over poor-traction road surfaces, such as loose dirt, pooled water, or ice. The system automatically reduces engine output and independently applies braking power as necessary to each of the four wheels to help maintain vehicle stability and driver control.

Traction control is standard on both four-wheel and two-wheel drive vehicles. Using the same wheel sensors used for VSC, the four-wheel drive A-TRAC system maintains wheel traction on slippery surfaces, by automatically applying brake pressure to each wheel, independently. A-TRAC adjusts braking influence to individual tire grip at all four corners.

Two-wheel drive models features TRAC, a system similar in operation to A-TRAC, but dedicated to rear wheels only. One major difference between the two is that the A-TRAC system is full-time, whereas the two-wheel drive TRAC system is defeatable. This feature gives the TRAC system an added measure of engine torque in sandy or muddy conditions at low speeds.

 

'01 owners manual, page 115, second paragraph, last sentence of section "L4" mode (low speed position, wheel drive, center differential locked):

"In the following cases, the output of the brake can be controlled by the active traction control system if the enigne speed is under 3000 rpm (normal engine speed is under 3000 rpm when the wheels get unstuck).

• The front drive control lever in the "L4" position and the automatic transmission in the "L" position or the automatic transmission lever in the "D" or "2" with the transmission downshifting to the first gear.

• The front drive control lever in the "L4" position and the automatic transmission in the "R" position."

This tells me one of two things:
1. A-Trac becomes disabled if in 4Lo/Lo (or automatically downshifting to "L") and the engine RPMs are over 3000.

Or

2. The A-Trac system remains active while in 4Lo/Lo, but cannot control wheel(s) spin when engine RPMs exceed 3000 (possibly due to excessive torque??).

I can't remember for sure since its been a little over a year now, but I thought I read somewhere in my web crawling that excessive RPM's in 4Lo/Lo disables A-Trac. I see if I can re-trace my steps...

I'll also try testing it myself since they're predicting snow [again]. Over 34" since the first of the year.... and counting.

 

What a convoluted manual!
Doesn't that make it sound like A-TRAC works only in 4lo/1st gear and 4lo/reverse? What about 4lo/2nd and 4lo/3rd?

It sounds to me like they could have more simply said:

The output of the brake can be controlled by the active traction control system when the following three conditions are met:

1. the front drive control lever is in the "L4" position AND

2. the automatic transmission is engaged in either 1st gear or reverse AND

3. the enigne speed is under 3000 rpm

Does that sound correct?