On some models of GMC trucks, the torsion bars control the ride height. These are long solid tubes of spring steel, splined on both ends, that connect to the lower control arm and the torsion bar keys on the frame. When the suspension compresses, it twists the torsion bar, which then unloads and pushes back, acting like a spring. You can remove these yourself, but if you don't use the right tools, you can hurt yourself.
Raise the truck with the jack and place jack stands underneath the frame to support all sides. Remove the front wheels using the tire iron.
Locate the torsion bar crossmember in the middle of the truck. Find it by following the torsion bars from the lower control arm at the front suspension, back toward the rear of the truck until it connects to the crossmember. Locate the torsion bar keys, which are in the middle of the crossmember and have a bolt running through one end. Install the torsion bar puller tool onto the crossmember so that the tool sits vertically in the crossmember, and the puller tool bolt is next to the torsion key bolt. Make sure there is enough room to use the impact wrench on the torsion key bolt.
Connect the impact wrench to the air hose and the air compressor. Remove the torsion key bolt using the impact wrench. Loosen the bolt on the torsion bar puller tool slowly to release tension on the key. Pull the torsion bar key off of the torsion bar, and then the torsion bar from the suspension.
