I don't know how hydraulic fluid would stay in the socket. My father has a 1985 300D and the Haynes manual for his car says to apply white lithium grease with a brush. The only lithium grease I had was in a spray can, so I also used heavy grease. I popped off the socket and put a good amount in each socket and popped them back together. Then I wiped off the excess. This seemed to quite down the linkage a bit.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member