My 1983 300SD had a slipping then stopped odo.
The same Loc-Tite type fix worked.

And when I opened it I found the 12 tooth gear was missing two teeth.
I scavenged a replacement from an old Radio Control toy car.

I found the internals to be basically the same as the earlier W123 odo.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250