If you can fix the transmission (and even if you can't) you can probably sell it on craigslist for more than $650. You will probably get the most money from parting it, but need room to store the parts and the shell while you do it, plus it would be a shame to see another W116 off of the road.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine