This is on a 85 300D: What causes a window to "chatter" when it is all the way up and you press the up button again?

I have only had experience with the Rear Windows. In my case it was because the Motor Gear Teeth (hard metal) were jumping on the Window Regulator Gear (soft metal) and I am guessing the Regulator Gear was springy to be pushed away from the Motor Gear; but not without damage.

See pics.
http://www.peachparts.com/shopforum/showthread.php?t=254722&highlight=Extreme

You will not know for sure what the cause is until you pull of your Door Pane. If you do under the cupped area where the door opening lever is there is one Screw. You cannot see it as a cupped/dished plastic piece covers it and needs to be pried out.

__________________
84 300D, 82 Volvo 244Gl Diesel