[James Lamb]

My 1989 Suburban has the rear tailgate and window, so not really the same, but ... a few years ago I realized the door latch posts on all the doors are supposed to have a plastic collar on them. Broken and gone for so long I did not even realize there was anything missing. I found some pex pipe the right size, cut lengths of pex, slit them, forced them onto the door latch posts, including the tailgate ones. In general that cut down a lot on rattly noises, and the doors no longer have a sag. It's cheap - one piece of pex is a couple $, might be worth a try.

Also, my rear window had a ding on the top edge of the glass when I bought the truck. Finally took the rear window seal out to find a row of body bolts holding on the rear top edge of the body, including the rear rain gutter. One of those bolts had backed out. They are Torx on my truck, so I used my impact driver to torque the crap out of all of them to insure no more backed out. If yours did something like that could the bolt head by hitting the door at bumps?