[datguysaL]

well wat could of happend was that whoever had the truck before, did some damage to where one of your front wheels was pushed back, and they could of just corrected it pushing the rear axle back or foward from one side, and the aligment machine is not catching it since its measuring the wheel angles only.

check your chassis for squareness.

get up under your truck and check to the lower control arm and that the rear axle are sitting in the slots, also check that the center bolt on your rear leaf spring has not broken and shifted the springs.