My friends 96' 4-door Blazer is having trouble with the rear glass closing and locking. He has the rear tailgate lowers and the glass lifts up style. You can push the button on the rear tailgate and hear the release noise but it's already released I mean it looks shut but when he's driving it pops up a little every time he hits a bump, it doesn't latch shut. Is there something to look for that I can fix or replace? I told him he might have to look for the entire piece thats in the tailgate at the junk yard. Just need some pointers on what to look at or do.

 

Your friend has the drop gate style.
My understanding is that the rear glass is popping-up when a bump is hit; is this correct?
My suggestion is to open the rear glass, drop the tailgate down, remove the plastic/carpet piece on the tailgate, have a good look at the latch mechanism. You should be able to "see" why the rear glass is not latching. It may be the entire latch needs replacing and your idea of getting one from a salvage yard is the way to go.

Good luck.

 

I second LannyL81's remedy. The latch might just be gummed up and need cleaning with a good solvent.