60 MPH is good, not much over if you plan to keep the car a long time like me .

The final drive swap is a good thing if you have a manual tranny and / or live where it's flat .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Mine would certainly do 75. But the engine was screaming so loud I used ear plugs sometimes. Ususally I'd try to keep it at 65 or below.

It's a pity the German market 5 speed is not easy to come buy. If you could find one it would be in Germany. So your only real option for longer legs is to get a diff out of a 300D or maybe a 280E. You just have to search and keep searching. I bought a replacement diff for my 240D but it wasn't a taller ratio. I just wanted a straight swap when I did my rear axles. I was intending to rebuild the whole rear end. If I rememeber correctly it cost me a couple of hundred.

No idea if it was any good though as my car grenaded itself before I could start the work. Had to scrap it a couple of months ago. So now I have a diff sitting uselessly in my garage. Pity its not the taller ratio or you might have a use for it.

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

oh, ok. So the swap doesn't do much for the auto trans cars? Yes, 60 mph does seem like the upper limit, 55 is even better but that's pretty slow, these days. I use it, mainly, for my work commute. That consists of a mix of roadways: 55 mph Interstate and a bunch of secondary roads of 25, 35 and 45 mph (traffic lights, etc.). It's a 30 mile drive, one way. A nice mix and good the 240D isn't screamin at 60 mph the entire time.

You want to see slow? I have a 46 Plymouth P15. Top speed of 79 and the brakes seem like a wish. My 300d is a dream compared

Given the "autobahn pedigree" of these cars, it seems odd, IMHO, that 60 mph is about all they're good for. I wonder what MB had in mind for general/intended use? Grocery getter? Putt around the suburbs? Out to the country club for a round of golf then back home again? And, of course, taxi cab. It's a mystery to me....

There's nothing myterious about it. The 123 diesels were the latest in a long line of MB diesels going back to the 260D of 1936. They were never autobahn stormers, they were "relatively" cheap exceptionally reliable transportation for the middle class of Germany and the world. Many were used as city taxies in Europe (and now various north African locations) where top speed simply wasn't of relevance. The diesels of the 50's and 60's, the Pontons and Heckflossen were even slower. The 115's almost as bad. Nobody back then who bought these cared about off the line performance or top speed, especially in Europe. And in the US the speed limit was down to 55.

If you wanted to storm the bahn, you bought a gasser, especially a six cylinder W114, followed by the W123, 250, 280 and 280E.

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S

This is not true.

I regularly take 9 hour trips up and down california at 70Mph.
I used to do 75mph but found that dropping 5 was better for fuel economy and significantly better for taking phone calls.

People like to use the verb "scream" to describe the sound of the engine at higher RPM
I forget the psych experiment, but briefly showing participants a photo of a minor fender bender and later asking them to recall what they remembered seeing, was greatly impacted by whether the psychologists used the word "smash" or "crash" to describe the accident. All participants primed with the word "smash"
recalled seeing shattered glass (there was no shattered glass). "Scream," I think is a bit histrionic.

And to your question about changing the differential, yes, it makes a huge difference if engine noise and rpms are your concern.
There are plenty of videos on youtube where you can see exactly where people are shifting with a 3.07 diff. It's much later than with a 3.69.


-

__________________
1981 240D 4sp manual. Ivory White.

Exactly...if the motor is sound. I used to always set cruise at 73 and go.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Didn't mean to offend anyone by using the incorrect verb or to mischaracterize exactly "for what" the 240D was originally intended. Just tryin to make conversation and understand a little more about my car. Admittedly, my experience is very limited. Without a tach, kinda hard to know what the engine is really doing at 60 mph.
I didn't mean to imply that I'm the "final word" on the capabilities of these cars, or ANYTHING like that. Just slammin away on the old keyboard while doin 10 other things..... My wife absolutely HATES my 240D, BTW. The "adjective" she like to use is "disgusting". Says "it smells like and old car and vibrates too much" LOL. As far as the latter, you'd think that'd be a good thing for opposite sex hahahaha.
Anyway, I'm perfectly happy "toolin along" at 60 mph. I'm too old to "be in a hurry" anymore. I really like my '83 240D and REALLY enjoy driving it. For some reason, which I can't quite put my finger on, it's really satisfying to own. As for the "mystery", again I wasn't being literal. I guess I just always, incorrectly, assumed MB and the autobahn equal somewhat fast cars.
Live and learn. I might be an "old dog" and it takes me a little longer to learn "new tricks", but, I'm always interested in learning and knowing new things.
I feel as though I got pretty lucky with this one (my first and only). I'm just the 3rd owner and the car is pretty much (very much) all original. Everything works, too! It's not perfect or pretty and definitely needs some work. But, it hasn't been all modified or altered, as in made to run of WVO or EVO or DEVO (sarc) or whatever, which I have ABSOLUTELY no interest in pursuing. That truly seems like a nightmare IMHO.
No cheap, gaudy chinese Pioneer "head unit" has been installed (original Becker cassette) No extra amps or speakers or USB, Bluetooty, etc. etc. ad infinitum. All the mechanicals seem original, too.
I recently got a '97 E300D which my wife likes very much and has yet to comment on "the smell". So, all good!
I now have 2 MB diesels on which to share my affections....

With a 3.69 axle it's around 3100 rpm.

I cruised at 3500 rpm 80 miles daily in my old 240d automatic no problem.

Made me feel like im on the autobahn with all that revvy engine sound

Hey now, that's good to know! Thanks, "christuna". 3100 doesn't seem so bad. Not being used to driving old diesels, I guess the sound of the engine, in general, can be misleading.
Kinda spoiled driving muffler'd gas burners and not used to all the "racket" (sarc)
Just outta curiosity, how long did you have that commute of 80 miles? "No problem" meaning the car was fine doing that on a regular basis?
Definitely puts my mind a little more at ease. I'm absolutely gonna enjoy my cruise more and probably give 'er a little more fuel in the process!!

In a 240D about 3 years.

I got rid of the 240D because after a few north east winters the car became a fred flintstone car (could see the road through the floor).

Then I got a 300SE that I cruise at 3500-4000 rpm (3.46 axle). Went cross country in it at 4000 rpm all the way with a/c on and nothing broke. Though it did leak/burn a quart of oil every 1500 miles

I hear ya on the "fred flintstone" thing...lol. Mine also has floor rot. It was repaired by the PO and not done properly. Dry and tight for now. Maybe in the future I'll have a piece of floor pan welded in properly. Mine has been a Pennsylvania car it's entire life. Can't believe it's not a whole lot worse than it is. One spot, left side of the driver seat.

Mine came to me basically rust free. I take it off the road from First snow till last. Or if there is a streatch of warn weather and some rain. I had alternator belt problems and finally got the belt fitted. I put on a larger alternator. Anyways drove it in to work today. Probably 60-65 mph on flat country roads. Need to replace the radio. Wish I had a Becker to upgrade. Its sort of a Zen type of vehicle.

I live deep in the high mountains of the West and my manual tranny 240D is a real joy to drive at speed since I put in a 3.07 rear end. Top speed is over 90 now and very quiet at 65-75. Fuel economy went up 2 mpg driving at 55-60. The only disadvantage is starting out in first gear or reverse which is slow and uses more clutch disc. Mountain passes are not slower that I can tell. Acceleration is of course slower as well. Speedometer error naturally. Actual speed over ground is about 1.25X indicated so if it says 45, I am actually going 55. Cost was minimal, about $160 for a low mile 3.07 and about 3 hours under the car on a lift. The '85 2.88 would be way too tall IMO. Worth it so far.