I think Tom is referring to the rear sway bar links. My w124 wagon does the same thing. I swapped out the rear sway bar links (based on suggestions here) and in my case it didn't help. But perhaps you will have better luck. It is a really easy job.

Lift the car, remove rear wheels, remove old part (2 bolts), insert new part, etc. etc. There was a plastic cover that had to come off part of the suspension, and that took the most time for me.

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1968 220D, w115, /8, OM615, Automatic transmission.
My 1987 300TD wagon was sold and my 2003 W210 E320 wagon was totaled (sheds tear).