I have a 1987 Monte Carlo LS. When I closed the door I had the dreaded window rattle. I was able to reduce this greatly by doing two things. First I replaced the dry rotted window sweeps. I purchased them from Mikes Monte. They came with the chrome trim on them and all the holes pre-drilled. Next I set the window stop so that it left the window about a 1/4 inch higher in the door when it was rolled down. This allowed a greater portion of it to be supported by the sweeps when the door was closed.
This did not solve the issue 100% but greatly improved on the initial issue.
This did not solve the issue 100% but greatly improved on the initial issue.