[zzrv]

Darby, here is what I found and I think to be the source of the rattle. The upper channel that the sliding window rides in has no weatherstripping or 'soft' channel to ride in. If you open your window, you will find that there is a LOT of vertical movement . The upper channel is very narrow, but I will check with my local RV shop tomorrow to see if he has any type of window weatherstripping channel that will fit in there.