1957 220S rear differential not working. Is there an "adjustment"?
 

Is there any sort of external adjustment on the application mentioned? I've got a friend that has a pristine 220S that the input to the differential is not doing anything. You can start car, put in gear, let clutch out and the driveshaft turns but it does not do anything. Also, you can put it in neutral, roll car back and forth (engine off, neutral) and the driveshaft does not turn. Is it a matter of needing a rear differential rebuild or replacement? Are there any keys that could shear? The owner mentioned that years ago it was making a good bit of noise and his mechanic at that time was able to adjust the noise out.

Any thoughts are appreciated

I'm just guessing but it sounds like the diff is internally broken.

Try posting in the "vintage" forum, the people there probably know more about it.