I hear what you're saying. My Tundra breaks the rear drive tire(s) loose a lot on wet roads, empty, and even on dry roads. Even at freeway speeds, at times. And it's not like the tires just spin, the ECU cuts fuel. This sucks. Although a minor complaint to some, it is my biggest complaint with the truck, besides the small fuel tank.
My 2003 GMC Yukon XL, which was a 3/4-ton, had 4-auto and it was great. The 4wd was partially engaged, and sent power to the front wheels when needed. Had an old Exploder, and although clunky, the 4-auto was functional. The owner's manual even stated that unsual noises might be heard from the drivetrain
I think the heavy duty trucks and Toyota skipped the 4-auto feature as they couldn't make it robust enough. But that is just my guess. I've heard that transfer cases with 4-auto are more difficult to make durable.
My solution for the Tundra would be to install a cone-clutch, limited slip. But, I don't know if it would be as good as 4-auto.
