I had a leak in my 93, I found the top of my windshield was letting water in, and it was running across the top of the windshield frame, then down the a-pillar trim, to the floor. I had a chip in it so I got a new one put in because my insurance covered it.
When I went to the glass shop, I was told that on the 88-98 style trucks, there is a pinch weld under where the top of the windshield seals. This pinch weld gets surface rust on it, and as soon as it gets bad enough, it pops the adhesive away from the metal, I was told that next time I get a chip, to take my truck to a body shop, have them blast, then prime and paint the top of my windshield frame, then have the new glass put in.
In my experience I won't use silicone on my glass seals anymore, it just causes more problems, expecially when you try to fix it correctly...

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93 Blazer- 216K, 350 TBI/4L60e/3.42 G80, 2" blocks, TB crank, 285 BFG A/Ts, Bilstein HDs, Flowmaster 50...
74 Impala sport coupe- 55K, 350/TH350, Edelbrock, Holley, Pertronix, Bilstein Sports, true duals, BFG T/As, Rallys...