I'm guessing the AT have speed sensors on all wheels and adjust the transfer clutch pack accordingly. Therefore if one wheel is always turning faster it may drag the clutch to try to compensate, thus burning it out.
As for MT, there are no wheel speed sensors and the front or rear differential balance out the difference in speed such that the two drive axels are still turning at the same speed.
Yes, I know the doughnut is the same diameter, but being skinnier I'm sure it deforms more, beyond the 1/4" circumference allowed for.
-- Dominic Richens | snipped-for-privacy@alumni.uottawa.ca "If you're not *outraged*, you're not paying attention!"