Some trucks have been so abused that the frames can be tweaked just enough so the bed isn't square when you measure both diagonals even though everything looks fine. This is mainly with the newer trucks that have a bed mounted directly to the frame, such as '60 and newer unless I'm mistaken.

Otherwise, there can be any number of tiny things that can cause it right down to a worn suspension on one side.

Jeff


My 1953 Chevrolet
1947.1 Gallery
1972 C-10 1/2 Ton & 1972 C-30 1 Ton