GM Service Manual Online
For 1990-2009 cars only

The following components are supported by a front crossmember frame which is rigidly bolted to the body rail at 4 locations:

    • Engine
    • Transmission mounts
    • Front suspension lower control arms
    • Steering linkage

The following components are supported by the rear suspension frame which is attached to the body rail through rubber insulators at 3 locations:

    • Rear differential
    • Rear axle
    • Rear suspension components

The underbody frames must be properly aligned to maintain the correct suspension and wheel alignment.

Warning: Refer to Approved Equipment for Collision Repair Warning in the Preface section.

The individual underbody components contribute directly to the overall strength of the unibody. Use proper welding techniques during service repair operations and for welding information and for vehicle preparation.

The components must be corrosion protected whenever body repair operations damage or destroy the original sealing surfaces. Use a two-part catalyzed primer such as PPG DP40 or equivalent when corrosion protection is needed to welded surfaces. Apply the sealers and anti-corrosion materials as necessary. Refer to Anti-Corrosion Treatment and Repair. Do not combine paint systems. Refer to Basecoat/Clearcoat Paint Systems for further information.