I have a 2000 zr2 blazer with a grinding noise in the rear end. Thought it was the brakes because when I got home, the left rear tire was smoking. Pulled off the Caliper only to see that there was still alot of pad left. Pulled off the disc and found the entire inside coated with oil. Now here's my question. It would only grind when I would brake. That's why I assumed it was the pads and possibly the rotor. Is it because the pads were coated with oil that caused them to grind on braking? They are semi-metalics from autozone. yea I know, cheapies. Or have I got something more going on here. Truck has 200k on it. Axle going? Thanks.

 

sounds like something more than brakes. with the oil on the inside of the rotor, i would say that you lost the axle seal and thats where the oil came from. the grinding could be the bearings on that end. if its what i am suspecting, you better get it fixed very soon other wise you will be buying more parts than you need. if its grinding the bearings into dust, then all that stuff could be making its way to the ring and pinion gear, which could cost more money.

 

Pretty much what I was thinking. Get the bearings and axle seal fixed, go ahead and do both sides, not just the one with the oil on the rotor. Probably a good idea to change the gear oil after, too. In case there was any debris from the ground up bearings floating around.

 

My only question though is why does it only grind on braking? When I'm at speed there is no noise (not that I'm aware of anyway). I can hear it coincide with stepping on the brake pedal. Foot off the brakes, no noise. Step on the brakes, noise. Wouldn't a bad bearing get louder with speed?

 

Not necessarily. I know that on the front, sometimes you can only hear a bad bearing while turning. The weight shifts, and the bad side will grind when you turn the opposite direction. You can drive straight all day at any speed, and not hear it.

You would think that being in the back, it would make noise under heavy acceleration, when the weight shifts to the back. Maybe the act of breaking puts some additional stress on the rear?

Either way, finding oil all over the rotor leads me to think the axle seal is bad. And while you're doing the seal, might as well do the bearing!

 

I have to concur with the above. We actually just repaired this exact same problem on one of our cement mixers today. You're going to want to get on that, like yesterday. Very bad news if you let it continue on.