Thanks for the above information Clemens and Ruut.
The background to my question is that I just started some back ground work, to prepare for some articles on the CX-type Morgans. All this for the Dutch Morganclub magazine (FataMorgana), of which Ruut is the editor in chief. I just finished my third article on the Roadster. Now, with the PlusSix being discontinued, I thought that I could start working on another discontinued Morgan model: the PlusSix. Ruut however, pushes me to included some PlusFour info in my writings them too. Ofcourse this has nothing to do with Ruur owning a PlusFour himself… For me doing the research is most fun thing to do, I did not deny his request (yet).
So when exploring, I could not readily Identify which manual gearbox MMC employs for the PlusFour. However, the above feedback from Clemens (“it’s a Germer box”) confirms what I have found myself in the meantime, by using ChatGPT to identify the gearboxe with exactly the same gear ratio’s as in the PlusFour.
My current working hypothesis is that MMC employs the GS6-17BG transmission. This is a manual gearbox (as designated by the S), it has six forward gears (as the 6 indicates). The 17 indicates that this is, what BMW calls an I-350 turbo gearbox. The B in the name tells us that it is designed to work in combination with a gasoline engine. The last G indicated that Getrag is the manufacturer.
The GS6-17BG transmission is specifically designed for turbo engines. I found that the BMW 328i (F30) uses the same gearbox. Note does not use the B48 engine, rather it has the N20B20. This gearbox is designed to work with a maximum torque of 350 Nm. Hence, that the engine in the manual PlusFour is tuned down to that level whilst the B48 engine delivers 50 Nm more in combination with the automatic gearbox.
