Hi
The foot (= kind of ball joint) of the hydraulic shock is aluminum, and they are known to wear out. Only solution is a new one. One does not need to replace them pairwise. It is possible that they were weak before and that working on the system (ie disturbing them, twisting them out of the way) has killed them. It is worth doing the upper mounts first, they may give such sounds too if they are bad.
I am at the same point, except that I did exchange the upper rubber and it did not help.
Good luck, Bruno

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1992 300TE 160 kmiles