One problem related to suspension torsion bar has been reported for the 2004 GMC Sierra. The most recently reported issues are listed below.
While driving at 5 mph or greater,and when turning left, there was a loud popping noise in the front suspension. Owner took the vehicle to the dealer, and was informed that the front torsion bar, and the left control arm came out of place. Also, the front cross member brace came loose.