Greetings! I've had a '71 280SE 3.5 coupe for 15 years. She's a euro model, with 4-speed manual trans, geared so steep I swear it'll almost climb a tree. Since the engine is a M116 3.5 V8 I was wondering if any (later) models (SLs, etc.) may have had a 5-Speed manual I could find to replace my 4-Speed? Hopefully, a straight bolt on with no mod. Would be great to shift into 5th and drop the RPM a little on highways. Many Thanks for ideas!
I am not well versed in the 1971 Mercedes-Benz, if only because it has been on this earth longer than me!
I am also not aware of a 5 speed transmission that would be a direct fit for your vehicle. You mention the vehicle is a 3.5 M116 V8 and I was un-aware that they even had a 3.5 V8.
The M116 is also an engine designation for 1986-1991 Mercedes Benz 4.2 liter V8's so I am wondering if possibly that engine has the same mating points as the later engine. Yet even if it did, the only manual transmission that I have seen with a manual (In the W126 chassis mind you) is the inline 6 cylinder.
Sorry I could not be of more help, however I am very much interested in having a look at this 3.5 M116 engine. Might you have a photo of the beast?
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Hopefully, a straight bolt on with no mod. Would be great to shift into 5th and drop the RPM a little on highways. 
