This section contains information on unitized body construction incorporating integral front and rear frame side rails.

The engine, front suspension lower control arms and steering gear are supported by a frame which is bolted to the body through rubber insulators at the four locations. Two rubber insulated struts secure the engine to the upper rail of the engine compartment front panel.

Mounting provisions for the front suspension system are shared by chassis components, suspension lower control arms and frame, and body components, engine compartment side panels. The underbody must be properly aligned to maintain the correct suspension and wheel alignment.

Individual underbody components contribute directly to the overall strength of the unibody. Use proper welding techniques during service operations. The components must be corrosion protected whenever body repair operations damage or destroy the original sealing surfaces. When needing a general corrosion protectant, use anti-corrosion compound GM P/N 12346225 or equivalent.

Vehicles involved in an accident of any nature which might result in a damage frame should always be checked for proper frame alignment in addition to steering geometry and wheel alignment. If the frame is damaged and needs to be welded or straightened to correct the problem, it is recommended that the frame be replaced. Do not attempt to repair the frame.

Improper frame insulator installation may result in the following noises:

The above problems can sometimes be caused by the wrong part being installed or the insulator not being properly tightened. Squeaks may be caused by an improperly located insulator rubbing on the frame rail.

If a problem has been diagnosed as an insulator problem, a color code check of the insulators to determine correct usage of a body bolt torque check can be performed. Both the upper and lower insulators are orange. If the wrong insulator is used, it must be replaced with the correct part.

The removal of any 1 frame insulator requires the loosening of the adjacent frame insulator to permit the frame to separate from the body. Be careful not to damage the fan shroud, steering hoses and brake pipes during replacement of the frame insulators.

When installing a frame insulator, make sure the lower insulator is fully seated into the frame. The frame insulator should be lubricated with rubber lubricant GM P/N 12345884 or equivalent. The upper insulator is pressed into the lower insulator sandwiching the frame between the 2 insulators. The bolt is the inserted through the mount, capturing the lower retainer. Do not overtighten a frame insulator. When frame insulator bolts are removed, you must replace the bolts with new bolts. If the frame insulator bolt does not thread in smoothly, it may be necessary to run a tap through the frame crossmember nut to remove any foreign material stuck in the threads. Be careful not to punch a hole through the underbody with the tap.

Check the frame-to-body alignment by inserting a 19 mm (3/4 in) guide pin or drill bit into the frame-to-body guide pin holes. If the guide pins will not fit, the frame is not in correct alignment with the body.