1redta

I have a wierd shimmy in the rear of my truck ( K1500 98 ). It happens when I hit the brakes especially 50-40 and makes the rear end shimmy. It started after I changed the rear brakes, new shoes and drums, and I don't know why. I rotated the tires which are fairly new and the shimmy is still there, I even took the drums back to the auto parts store and exchanged them incase they were warped or out of balance and the shimmy is still there I don't have a clue what to do next, any help would be greatly appreciated Thanks Art