Cool. Hearing that you’ve got hills, it’s possible you would have ended up cooking your clutch quickly. It’s possible we will never know. 3.46 seems like a pretty good all-around ratio.
My 1985 280sl has a 3.58 and it will get up and go, but it’s really not like the 3.69 that was in my 1981 280slc 4-speed. I found myself often trying to shift into a non-existent 5th in the 3.69 with no OD. Here are the ratios.
While with the 3.58, I find myself very often running in 4th on the highway for the extra power. Here are the ratios on that car:
I notice the slower acceleration in all the first four gears with the 3.58, and that 2.91 final OD ratio just doesn’t seem to have the guts, even with the m110 185 HP motor. Sure, I will eventually get past people on the highway, but it is laborious in comparison to today’s cars. This may be why I find myself leaving it in 4th quite often.
The 3.58 1:1 is pretty comfortable for cruising, more-so than the 3.69. That’s with the nicely revving m110 DOHC gas motor. I don’t know whether the diesel feels like it would be ready to shake itself apart at higher RPMs (not having ever driven a MB diesel).
In any case, I’m going to say, 2.91 is too low (and notice it’s not much lower than 3.07). 3.69 is not horrible, but certainly leaves me wanting a lower gear. 3.58 is pretty damn nice.
I’m thinking you will be pleased with the 3.46.
Hopefully you won’t find yourself having to go to third (1.45 probably) very often. That’s the equivalent of 5.00 with a 3.46, the same as the 3rd (1.398) in my 1985 280sl 5-speed. It’s not so insanely high that you won’t use it for passing, but hopefully you won’t find yourself “living there” because it would defeat the purpose. You might ask yourself how much time you already spend in 3rd gear with your current 3.69. If it’s a lot...
Maybe get your hands on a 5-speed 717.4xx transmission which will probably have ratios like mine. Or just get a 300D turbo motor. [emoji6]