Hi Dave,
There will be some wooden spacers between the frame and the bed...usually they are simple pieces of oak about 3 inches square into which a hole has been drilled in the center. If one of those breaks, it usually cracks at the hole and then it can fall out...leaving one side of the bed (usually one corner, really) leaning downward. If the bed hasn't been hit nor damaged I'd look there to see what's happening. Good luck.


~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end