I have an issue with my windows, 1981 Corvette. They switches and motors seem to work fine, they go up and down easily. They wont start to go down if the doors are closed unless I give the Window a little pressure downward, and if the doors are closed they wont roll up all the way either, they stop when they hit the weather stripping about 1/2 inch from the top. I can open the door and they roll up all the way and then I shut the door and its a good seal, accept right at the back of the window where there is always about a 1/4 inch gap that sucks air. Anybody got any clues as to why it doesnt seem to have enough power to start and finish on its own, or what may be the cause of the gap at the rear? I though may be the T Tops needed to be adjusted down in the back but I read in the maunal that they are supposed to sit up higher and not to adujst them. I also wondered if some of the nylon window roller bushings are worn out etc. I have replaced all of the weather stripping.