I doubt the idea of bad shocks. When I had similar problems, it was due to worn trailing arm bushings. There are two on each arm and it is difficult to see how worn they are until you remove the bolt and lower the subframe. In order to do this, you will need the MB spring compressor and I used 3/4 dr. sockets with a length of 5/16" all-thread, washers and nuts to press the old bushings out and reinstall the new. I used KY to lube the bushings for reinsertion as it is water soluble.

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Sam

84 300SD 350K+ miles ( Blue Belle )