I have had a problem with my driver's side window ever since I bought my 89 last summer. I tried to dig into it today to take care of the rattles and what not. No matter what type of adjustments i made, powering the window down from full up starts with a mechanical pop, and with the window partway down, I can grab the front and back edges and rock it back and forth as if it is only attached at the bottom center. Trying to tighten everything up, I just can't get rid of that movement. All the rivets seem to be in place and tight. My guess is that the regulator is worn out.

I think I have found the mechanical "pop" when the window starts down from full up. I have a stress fracture on the upper rivet to the regulator, when the window is full up, it pushes the door panel in somewhat and and it moves the two edges of the crack. When the window starts down, the metal snaps back. Something I'll have to fix when removing the regulator. I still think the regulator is shot.

Here shows the crack on the upper rivet where the regulator is mounted. The lower rivet is not cracked, just a gouge in sheet metal.