I dunno, tgatch, but my co-worker (a fellow engineer no less) swears she gets 30+/- mpg in mixed driving around town and as high as 38 mpg on long highway trips from Seattle to Bozeman to visit her family. She says her old Benz gets as good of mileage as the Geo Metro she used to have.....
Has she actually calculated the numbers? Is her odometer accurate? An inaccurate odometer is not an uncommon problem with these cars, although they tend to read too low (or fail completely, when a plastic gear breaks) as opposed to too high....wouldn't surprise me, though. I can't recall ever hearing of anyone who's EVER gotten over 30 mpg out of a 123. Is she topping off the tank every time?
So if the 4-speed manual tranny out of a 240D will bolt up to the 3.0 liter in a 300D, I guess the only real issues with the swap would be the pedals and the driveshaft. Does anyone know if the 300D automatics have a removeable pedal assembly that could be taken out and replaced with a twin pedal assembly from a 240D stick shift? I know that the 300D was available with a manual tranny in Europe, and of course the 240D was available with both types of trannys.
So I would expect the pedal(s) and mounting bracket to be a bolt-in piece for both models for manufacturing simplicity. If that is true, then the big question is: are they the same piece for both cars so they will interchange. Aslo, what type of clutch actuating mechanism is in the 240D - hydraulic, cable, or mechanical linkage? Anbody know for sure?
The clutch actuating mechanism is hydraulic...IIRC, it taps into the brake master cylinder reservoir (not sure how) for a source of fluid. Regarding the pedals (as well as the gearshift lever, etc), it's all plug-and-play...you'll need to swap out the pedal assembly, but it's bolt-to-bolt; no fabrication needed.
I've never seen the two side by side, so I'm not sue, do the early 80's 240D and 300D have the same body, or is the 240D actually a smaller version? Another thing I was wondering about is the possiblity of installing a 3.0 liter from a 300D in to a 240D body that already has the manual tranny installed. Is there room enough in the 240D engine bay for the 5 cylinder?
A '77-'83 240D and a '77-'85 300D are an identical chassis...the only difference, besides engine/tranny, is interior appointments (automatic climate control, power windows, etc on a 300D). In fact, most people prefer to take a 240D and put a 5 cylinder engine into the car, because they prefer the more utilitarian 240D chassis (with manual climate control and manual windows, and sometimes a manual sunroof). If you do that, I'd recommend also swapping the differential (simple swap), because 300D's have a numerically lower gear ratio than 240D's...I don't remember the 240D's gear ratio (I think it's in the 3.73 range, but don't quote me on that), but '81-'84 300D's have a 3.07 rear end, and '85 300D's have a 2.88 rear end. IMHO a 617 turbo is happiest cruising between 2400 and 3000 RPM...with 2.88's and a slushbox, my old '85 300D was right at 3000 RPM at 70 mph. I got about 25 in mixed city driving, and could break the 30 barrier on the I-5 at 70 mph if I was careful.
BTW, this probably won't be a problem, but just in case...don't try to swap a '77 or later engine into a '76 or older car, or vice-versa. The base block is the same, but many of the external accessories are different...most notably the oil filter assembly. Might be possible to trade assemblies, but I'm not sure...and, by the time all was said and done, it'd probably be more trouble than it's worth. Also, if you really want an automatic climate control setup, I'd strongly recommend using an '81 or newer chassis. The '77-'80 ACC setup is very problematic, and VERY expensive to repair. The 240D's manual climate control is far more foolproof, but the '81-'85 setup's actually pretty good IMHO...
Hope this helps some
