mine had a rattle coming from the passenger side rear window also. it ended up being broken tab on the outside chrome window trim that caused everything to bounce around in there and rattle like crazy. i could push on the chrome part, like where the top and bottom come to a point at the back rear window, and it felt "mushy" i guess is the best way to describe it. i could tell something wasn't holding it in right. the dealership ended up ripping all that out, which includes taking out that rear window because it is all attached and had to be resealed by a window company they outsource to. no problems now though. maybe check that out?