Enter your question. When I back up first thing in the morning I hear a growling or grinding noise. My mechanic at first couldn't hear the sound but he changed my front brakes and rotors. Still the noise. This time my mechanic said that he heard the noise and took my back brakes apart and found nothing. He doesn't know what the noise is, however, it is getting louder and louder as time goes by. Any ideas?
If he didn't hear the noise, why did he change the front brakes? Was he having a slow day?
GM has a problem with slow seepage from the rear wheel cylinders that makes the brake dust moist and embeds it into the brake shoe causing it to grab. You can usually identify this by the brake dust getting darker in color and the brake shoes getting shiny. If this is the case, the shoes and wheel cylinders have to be replaced and the drums have to be resurfaced to resolve the problem, no shortcuts.