When accelerating from stop, at about 15 to 25 mph, the traction control would come on and I would loose all acceleration; in a few seconds the drive train would again come on and the vehicle would lunge forward as it continued acceleration. This would happen about 20% of the time. Had it to GMC dealer three times before they found the problem. In the mean time I would turn off the traction control.

The third time the dealer was able have the defect code reader in place when the problem occurred and it turned out that the LF wheel speed sensor was dropping out and was slow to respond causing the traction control to engage and loose power to wheels. They replaced the speed sensor and wheel hub bearing and this seems to have fixed the problem.

Mainly reporting this because it seems that this problem is quite common on Yukons' at about 70,000 miles and it could be a serious problem if you pulled out into traffic and your vehicle stopped because of this problem.