C'mon .... you've been around here long enough to know that you can do a search to get that info...

However - yes, you must replace the timing chain when it's excessively stretched, no, it's nothing like the M117 where the chain slowly self-destructs. The older OM617 engines may go their lives without a chain swap if the oil's been changed aggressively enough. The OM 60x should be changed around 4 degrees of stretch, the OM617 is a bit more tolerant of stretch. On these you can either pop in a woodruff key or swap the chain. Since you have to do valve adjustments on the OM617 anyway, it's easy to keep track of the stretch.

Good luck with your diesel.

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Tjohn

82 300 SD
77 450 SL (gone)