Is it possible to replace a 300d w115 auto with a 300d 123 auto? how about a 123 240d stick?
i beleive my auto is going out, and i can get a helluva deal on the 123 auto. If i can scrape up some money i would rather go with a 4 speed.

Auto, no. They use different controls.

Manual, yes. There are threads about auto-manual conversions if you search.

interesting... i would have assumed the auto would be a simpler swap.
So it is possible to put a w123 stick into the w115?
what differences from the w123 to 123 vs 115 to 123 swap?

I'm not so sure. The early (pre-1982) W123 300D tranny should be more or less the same animal as the W115 300D tranny. They ought to both be 4-bolt pans- 722.1xx. Am I missing something?

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80 300SD (129k mi) 82 240D stick (193k mi)77 240D auto - stick to be (153k mi) 85 380SL (145k mi) 89 BMW 535i 82 Diesel Rabbit Pickup (374k mi) 91 Jetta IDI Diesel (155k mi) 81 VW Rabbit Convertible Diesel 70 Triumph Spitfire Mk III (63kmi)66 Triumph TR4a IRS (90k mi)67 Ford F-100 (??)