I'm wondering if anyone else hears a loud knock when they back up then brake. I was told by the dealer that this is normal grabbing for the rear brakes. I need to replace the pads, so maybe the sound will stop. But wanted to see if it is another problem.
Have they been replaced before? It could be poor fitting aftermarket pads or possible missing hardware (I'm not sure if that uses metal shims to hold the pads or not). What usually causes this is the pads moving in their carrier. They shift up & down as the direction of pull changes (forward/reverse). It usually happens the first time you hit the brakes after changing direction, either backing up or pulling forward.
I changed the rear pads and the back up sound went away. The pads were quite low and it was probably making the sound because the calipers had to go too far to grab. All is well....except maybe a little bleeding to be done! It was my first time changing them myself and I'm not sure that I'll be doing it again!