My rear quarter windows are squeaking constantly and they are about as loud as the exhaust. The chrome runs all the way around and bolts into the frame too. I figured this was the place to ask for products or reccomendations because nobody else cares!
It's a VW passat and the problem windows are the rear quarters which don't have any mechanism holding them in except for some bolts which go through holes in the frame. The noise is not effected by bumps, or weather conditions.
Window squeaking is a problem with many Porsches as well. If its a glass in the rubber or rubber in the frame scenario,(seems most likely) the solution on the Porsche forum has been Pedros Ice Wax. It's a waxy lubricant that can be fount at many bicycle and motocycle shops. It can also be mailordered from Bicycle merchandise sellers.
If it's a metal on metal squeek then you will have to narrow down the two offending pieces of trim. If you can't remove and put a buffer of electrical tape between them then start sliding a piece of paper between them until you find the spot where the noise subsides. Then work a small piece of felt or electrical tape between the two.
Gotta agree with Brad on Pedro's Ice Wax. While you're waiting for it to arrive I'd recommend you try a regular silicon lubricant spray. I have, more than once, been able to get a silicon spray to fix squeaks.