We'll after the process of elimination. I have come to realize that the vibration on the back of my 02 F150 HD, is from a missing shim/wedge between the leaf springs and the axel. So here is the question(s). Does anyone know anything about where to buy these things? And what thickness is needed. I looks as if the right axel is more tow-up (level) and the left is more tow-down (angled) Do I need to have more of a wedge or less of a wedge to increase the angle of the axel right axel to match the left?

Thanks