If I press and hold the TC button on my '11 duramax, it takes both TC and Stabilitrac off. After reading this thread I took it off on a wet road and got seriously sideways with both back tires spinning like mad. I did not detect any computer intervention. Could you guys be experiencing the torque management kicking in? This is different than TC. Torque management is what prevents you from stressing or damaging your transmission from too much torque.
