Check your rear axles for torn boots. If there are any, it is almost for sure that the CV inside is bad. If boots are all ok, then it will be a bit harder to tell for sure, but very likely one or more has gone bad. Lots of posts about what to do about replacement, just search for 'CV joints' or 'half shafts'.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150