A broken speedo cable is an easy fix, at least in my U.S. cars. Auto parts used to carry a universal cable you cut to length and crimp a square end on. But, in my case the cable didn't die, but was murdered. Culprit was a wobbly bearing in the speedo which caused the spinning cup to grab, so good the cable broke and spared the speedo (had it re-bushed). Never dug into my M-B speedos, so don't know what is in there.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans