1977 - 1978 Corvette: Service Bulletin: Rear Bumper Cover Wavy
Subject: Rear Bumper Cover Wavy
Model and Year: 1977 - 1978 Corvette
Source: Chevrolet Dealer Service Bulletin
Date: July 1978
TO: ALL CHEVROLET DEALERS
Some 1977-78 Corvettes may exhibit a wavy rear bumper cover above the tail lamps. This condition could be caused by the position of the rear bumper bar relative to the energy absorber. In January, 1978, the assembly plant started using a fixture to improve the adjustment of the bar, thus eliminating the distortion.
The appearance of a wavy cover can be improved using the following procedure:
1. Loosen the bolts which attach the rear bumper bar to the energy absorber assembly. See illustration. To remove depressions from the cover, raise the bumper bar. If the cover is bulged, lower the bar. If a satisfactory fit is obtained, tighten the bolts (70 Nm/52 ft. lb.). If the cover is still wavy, mark the bumper bar at the point of best vertical fit to the energy absorber.
2. Remove the lower two bolts on each side. Refer to illustration. Since the shims are slotted at the top, removal of the upper bolts is not required.
3. The bar is shimmed at assembly, but may not be at the optimum position. Adding shims (PIN 473279) will stretch the cover and removing shims will relax it. Shims should be added or removed one at a time.
4. When a satisfactory cover fit is achieved, tighten the energy absorber to bumper bar bolts.
Each site must be adjusted independently. Due to manufacturing tolerances, one side of the bar may have more shims than the other and be at a different position in the energy absorber slots.