My 1979 300TD wagon has wind noise at highway speeds coming from the driver and passenger side windows. If I move the window down slightly from the fully up position, it eases the noise somewhat. I suspect the window channel is the culprit, but I am not sure. The noise is sort of a whistle, and it only occurs at around 60-75 MPH. Anyone familiar with this problem, I would be most appreciative of your help. Thanks.