Noise at Torsion Bar Location/Cab Difficult to Open (Replace Pivot Torsion Bar)

This bulletin is being revised to correct the labor operation numbers. Please discard Corporate Bulletin Number 00-08-63-003 (Section 08 -- Body and Accessories).

Some drivers may comment about noise coming from the cab pivot torsion bar area during normal operating conditions or that the cab is difficult to open. The cab torsion bar may be found broken or may break while driving.

Corrosion may be causing the cab pivot torsion bar material to become fatigued and possibly break.

Inspect the condition of the cab torsion bars. If the torsion bar is severely corroded or broken, replace the affected torsion bar. The new torsion bars have revised material that should reduce corrosion. Use the following procedure and the applicable part number listed below.

1. From the front of the vehicle, loosen the torsion bar bolts and the support arm lock bolts. You should not need to remove the grille in order to access the bolts.
2. Tilt the cab forward. Refer to the Cab Tilting procedure in the General Information subsection of the applicable Service Manual.

•	After tilting the cab, pull the service pin on the cab tilt support and extend the tilt support full forward.

•	Install the tilt support safety lock pin.

3. Remove the support arm from the spline of the torsion bar.
4. Remove the tie strap retaining the electrical harness to the torsion bar if present.
5. Remove the bushing and slide the torsion bar out. You may need pull the edge of the bumper fascia slightly forward in order to slide the torsion bar out.
6. Do the following steps in order to install the new torsion bar.

•	Locate the identification marks before installation.

•	Match the spline.

•	Install the new torsion bar and bushing.

7. Secure the electrical wiring harness to the torsion bar if present.
8. Install the support arm onto the spline of the torsion bar.

Tighten

•	Tighten the torsion bar bushing bolt to 20 N·m (15 lb ft).

•	Tighten the torsion bar lock bolt to 37 N·m (27 lb ft).

•	Tighten the support arm lock bolt to 37 N·m (27 lb ft).

9. Return the cab tilt support to the previous position by removing service pin. Remove the safety lock pin.
10. Lower the cab.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: