The back passenger tire on my 88 is a little closer to the frame than the other side.The rim rubs on the frame only when the passenger side of the truck drops.Do you guys know what might be causing the problem and how do i fix it?
From your tiny avatar pic, it looks like you are running the normal 42mm offset wheel, maybe an 18" x 7.5"? If so, there isn't quite enough room between the wheel and the frame rail when the axle moves around. There isn't much you can do about it except maybe some small spacers. If you go too far though, you run the risk of rubbing on the fender.
i'd start by replacing the leaf bushings. they are only like $6 a piece from toyota. probably cheaper for aftermarket. or get some energy suspension bushings for a nice upgrade.