I have preemptively replaced the tumblers in both my 240's. They hung up periodically and what with all the warnings from forum members to deal with it before it was too late, I heeded them. Don't wait too long!
It is an easy fix.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily