Hi,
I posted about this a while ago, and thank you very much for your input then. Since then it's been an intermittant problem. Each time it goes away, I think what was done last fixed it, and then it comes back, etc. Actual hardware replacement to date has only been the flex disc on the front of the drive shaft. The rear one had no play in it. There were also loose bolts on the CV joint on the left rear axel. I have a buddy who is good with wrenches and he has the car now to see what he thinks. I got this email from him this morning.
"the wheel and bearings are tight and the noise is not coming from either of these assemblies.
I checked the oil level in the differential, checked the bearings with a stethoscope and rechecked all the control arms. Differential oil was fine. All the control arm bushings and bolts are ok. There is a very similar noise from the left rear if you slide the axle left and right, it hammers against the left wheel bearing. The right axle doesn't do this. I found no noise from the wheel bearing and only a very light noise from the differential, it matched the noise I heard on Saturday. I think it is the axle tapping on the wheel bearing. To take it one step further I would have to remove the axle and see if the noise goes away. By the way, the noise is on the left side, not right, of the differential and doesn't sound like a bearing. There is also noticeable run-out in the left axle, as if it were bent. The right side runs true.
Now that I have checked the brakes and wheels, driving it additionally will not cause further harm for the short term.
"Rebuilt axles" I have had a lot of experience with these. Some good, some not so good. There is a reason Mercedes does not provide repair parts for these. If the part fails under warranty, they are responsible. Typically, anyone would take the least expensive route to repair any problem. I have to think that if Ford and GM provide these parts, Mercedes would also if it were a good idea."