I have a 1998 F150 4X4, And for some time now everytime I apply the brakes my whole truck bounces. It isn't a pulsation from the rotors as I do not feel it in the steering wheel, pretty much all over. I replaced the rear shoes and drums thinking that maybe the drums were warped, well the problem is still there. I took it to a friend of mine that is a mechanic and he said that it appears I have something wrong with my ABS. Would ANYBODY know what may be causing this, I am at a total loss? Thanks