Chuck, things that go clunk in the night that are associated with independent rear suspensions almost always wear out more on the torque loaded side of the final drive. In the case of our common W124, it's the right. Having said that, remember that the diff and subframe are unsprung weight and a "clunk" associated with road surface irregularities is more likely to be a bushing on one of control arms or locator struts.

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Jeff Lawrence
1987 300e
1989 300e
1987 BMW 325