I bought a 97 F150 4x4 and the bottom leaf spring on both rears is of center from the others buy an inch. what caused this and what should I do.

 

Pretty common problem with any vehicle when the u bolts don't actually go over the springs but around the axle and then into the u bolt plate. Just hit them back into position with a sledge hammer without messing with the u bolts. If that doesn't work then loosen the u bolts a bit and then hit it with a regular hammer and it'll move pretty easily (make sure to retighten u bolts or maybe even get new u bolts to make sure you don't run into an old rust spot). This problem tends to happen more often with changing weather from warm to cold because the u bolts will expand and then compress due to temperature variations. BTW that spring is called an overload because when it's sole purpose is to stop the springs from bending too far down when overloaded. Some people call it an underload so it's not confused with a top overload aka auxilliary spring.

Edit: Usually helps if you take the weight off of the springs by jacking the vehicle up from frame or receiver

 

Check with your dealer, but I believe there was a recall on this, since some have ruptured the gas tank.

 

thanks for the tips