Arrggghh! The bearing again? Maybe? Maybe not?
 

OK, my 87 300E is at it again. 1 1/2 years ago I replaced the left rear bearing. It needed it. When the tire was jacked up you could really feel the play in the bearing. Now the rear wheel is grinding and graunching again. I jack up the offending wheel and grab the tire to test for play...there isn't any. It's solid. I test the passenger side, it's solid too. So I don't know what to think anymore. Could it be brake pads? Or differential mounts/bushings? Any ideas you have would be great. Thanks in advance.

It may be that your parking brake shoes have come apart.

Or it could be the service brakes themselves. I've been fooled more than once thinking I have a wheel bearing problem when it was the brakes that needed service.

I've never looked at the rear brakes. I replaced the front pads last year but haven't paid attention to the rears. The car is 17 years old...you think it needs rear brake pads already? ;) I think a disassembly is warranted. But man, it sure SOUNDS like a bearing. I'm glad the test showed otherwise. If it turns out to be the rear brake pads or something like that I'll thank my lucky stars.

I had what I thought was a squeally rear bearing. Turned out to a stuck piston on the right rear caliper.

OK, I replaced the rear pads. They needed it but nothing looked out of the ordinary. When I road tested the car the growling and squealing was still there. I need a psychic.

Isolate the wheel hub
 

Rearend noise can be hard to diagose. I once had this rumbling noise from the rearend, and did not want to run the car while jacking up to find the source. I ended up disconnect the half-shaft, so that I can spin the rear wheel hub by hand. Sure enough, the wheel bearing is the noise source. Don't know if this apply to your car.

Get a $10 dollar stethoscope from your local auto parts store. It will pay for itself immediately diagnosing noises like that, either in the back end or the engine area.

If I could make the noise appear while the car was jacked up with the wheel off it would be so much easier. Methinks I need to think about taking it to the shop.

Well RPM55 nailed it. I took off the caliper, then the rotor so I could look at the parking brake shoes. The rotor came off hard and I could tell it was rubbing on the brake shoes. So now we know what's making the noise but when I inspected the parking brake I didn't see anything out of the ordinary. The springs weren't broken and the shoes looked like they were in place. I wonder how they expanded? I turned the set-screw so that the shoes adjusted inward a bit but they still rub the rotor. Anyone know what the problem is with the parking brake? Could it be as simple as a cable adjustment? Hmmmm...