1998 3500 Brake problem

From : yvonne thompson

Q: i had my rear brakes checked about a month ago and discovered the left wheel had about 1/2 of the lining still left while the right side had a groove in the drum about 1/8 in. deep from the lining being completely gone and the rivets grinding into the drum. i had the brakes done including a new drum. about 2 weeks later i started getting a severe vibration when i applied the brakes. i returned the truck to the shop and they replaced the drum again thinking maybe the drum was defective. about 2 weeks later i again felt the vibration when i applied the brakes so i took it back again. the shop rebuilt my wheel cylinders again and bled the brakes to make sure the fluid was clean. guess what its doing it again. does anybody have any ideas of what could be the problem. i would very much appreciate any suggestions. thanks randy .