[chcknugget]

Originally Posted by wolfox

Yeah, they put in a beefier, +2 clutch and friction surface clutch in the AWD and automatic 4x4 models. I think the idea was to calibrate the clutches just a tad with a synthetic and friction modifier to allow just enough slippage on dry pavement, but decent enough torque lock-up in slippery road conditions. Kind of like a "poor man's" center differential that true, all-time AWD systems would have, but instead made out of mechanical parts barely slipping by one another. In *real* AWD systems, the center differential is merely a viscous coupling filled with a thick silicon type material, close to what they fill fan clutches with. Careful calibration of dissimular wheel/axle ratios front to rear kept the fluid in a slightly "warmed up state" but did not allow for more than 10%:90% rear to front torque ratios. When a wheel starts to slip, the fluid is under extreme pressure from the whirling surfaces that are mechanically linked by the viscous coupling causing it to expand even further, shifting eventually to a near 50%:50% ratio front to rear. Chevrolet/GM accomplishes this task through a mechanical system - or so I theorize - where the clutch packs supply a fixed amount of torque to the front wheels, all the time. When conditions are good, the tires' grip overcomes torque output just enough to allow smooth cornering. When traction is low, or in off-road conditions, the torque is enough to put just enough power to the front axles to get you out of trouble. Or so, my theory goes.

Now for the factual stuff I do know:

AllTrak II can be universally placed into Dextron-III applications. However, AllTrak II fluid specified in modern designs cannot be swapped for Dextron III. Dex just cooks to sludge within a few hundred miles from the punishment that the constantly slipping front differential output shaft clutches puts on the fluid. If you drain "blue" out of your transfer case, *PUT* "blue" back in it. However:

Is there a benefit of putting AllTrak II into a Dex-III x-fer case? Slight to minimal. It is a synthetic fluid afterall, but a better, more cost-effective use of alternative fluids will be better in the long-run. (Like Redline - How is it? My Transfer case is soaking in it now. Marinate for 60k miles, and exchange the fluid again) If it bleeds "red" you *can* swap "blue" back in - but AllTrak II costs nearly 3x as much as Dextron, and 2x that of any *good* synthetic product rated and put into Dextron service. And that is all I have to say about that. Goodnight, and don't forget to tip your waitresses back upright before you leave tonight. You've been a great audience!

When I changed to Autotrak II in my parents van it took me less than 4 quarts (I filled it, drove around 10 mins, then emptied and filled again) and at $3.00 a quart from the dealer it cost me a total of $12. It's hardly expensive when compared to Mobil 1 oil.