the driver's door window in my 01 Z-28 rattled badly when in any position other than all the way up or down. I did a search and found suggestions to adjust the two pads that push against the glass at the top of the door sill. Did that, and they actually were pretty well adjusted as I found them. I took a look into the door housing for lose parts and then put everything back together. Didn't solve the problem. What it turned out to be was the rear guide roller assembly. It is a pressed or wedged fit to the window support frame and it had worked lose. The thing has the guide wheel and then about 3/4 inch aluminum standoff. I took a dremel tool with a abrasive barrel shaped bit and ground of the back to allow removal. It leaves a 1/4" hole. I ground off the remaining protrusion were it went into the window frame. I drilled and tapped a 1/4" 20 hole and reinstalled it with a star washer and Loc-tite.

 

Good Job!
Many people end up replacing window tracks when the guides loosen up or wear out. The rear guide you are talking about is a very common problem on f-bodies. It sounds like you found a good way to correct your without replacing it.