Replacement gears are available from several sources. What needs to be known when ordering is what the tooth count is for accurate/reliable counting.

The drive pinion is always 12 point. Second gear is usually a 12/48 point. Third gear varies. Some are 12/48, some are 16/48. My '86 SDL is 15/48.

If you have the wrong ratio on the final gear, your ODO count will be wrong as well.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]