Help need opinion on rear brakes!!!

[*CuTlAsS*]

For some odd reason ONLY when I'm going into reverse and slowly applying the brakes it makes a really deep hollow sound that vibrates through the car from the rear brakes. Now my brakes are fine what else could be doing this?

[qwex]

check the adjuster on the rear shoes. it may be hanging or if you recently had work done put together backwards...it happens

[*CuTlAsS*]

I checked the shoes, they're on the right way, I know the balance is off, but it makes quite the sound occasionally when I'm backing up. It vibrates thru the whole car.