This is most common on late 1990, or early 1991 Corvettes and ZR1's.
Rear hatch glass is touching or almost touching the fiberglass lip near the gas tank flap on one side, but has about 1/4 inch gap on the other side. Additionally, if the glass has shifted down too far, the hatch latch striker may show signs of abrasion, and the plastic trim may be dented or broken.
Procedures and Cure:
If you have a really different (intermittent screeching / creaking / scraping) sound that the dealer cannot identify, combined with a mis-aligned rear hatch glass, it might just be a glue adhesive failure. You may find that the sound travels - seems like it is coming from different areas at different times. You may take the cabin back interior trim off and notice nothing loose.
Back in the days of the CAC, good old Jerry Watts knew what it was immediately. Jerry faxed a copy of the service alert #93-131-10 about the adhesive failing on the rear hatch. At first, I could not believe it since the checking procedure included opening the hatch fully and trying to notice a wiggling or looseness when pushing up further - which my glass did not seem to do (I wasn't pushing up hard enough). But Jerry was right about many other things, so back to the dealer we went. With the procedure bulletin in hand, the dealer took my car to the auto glass shop nearby where they removed the glass hatch, re-glued it, and bolted it back on - problem solved: $100 bucks, plus whatever the dealer charged for "diagnostic charge". Yes, the glue supplier had provided defective glue for a time period, and it was changed when the GM factory found out about the failures. I am not aware that one can do this repair at home since the glass handling is tricky and the hatch is very heavy and expensive. So, just take the car to a reputable glass business and instruct them to remove and re-glue the hatch glass.
The removal procedure, not the re-gluing, is described in the GM Repair Service Manuals ST-364, section 10-8.
by Randy Schulkers