Cheap fix for the 928 window rattle. I found out that the lower plastic guide over the black rod tolerance changes and as the gap gets wider the window starts rattling. I used a thick plastic zip tie wrap to close the gap took less than 10 minutes on each door. They come in different sizes from Home Depot or 99 cent stores. In the picture (taken from my camera phone) I'm pointing to it with a pencil. The good thing is you don't have to take the door panel off just pull the center cover near the door handle , tear the white nylon, and raise the window 3/4 up until you see the lower plastic guide and insert the tie wrap and lock it. I don't know how long it's going to last but it's an easy cheap fix and no more rattle. It has been 6 months and still no rattle.
1986 Porsche 928 32v 5spees 180k miles