Flex disc! Yes, I would look at both ends of the driveline for wear (one at each end) as well as the center support on the driveline. The flex disc is secured by a circle of bolts and would show stress tears in the rubber if faulty or if gripped you should not be able to move the shaft up nor down at all.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.