I have bought one sight unseen.
What is the highest maintainable top speed of an 82 240 4 spd manual on a flat roadway? The last 240 I drove was an auto and topped out at 70.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods

That would be w/ a/c on.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods

I think the 4speed manual ones with a healthy engine can hit the upper 80's to near 90mph, the manual puts a lot less drag on the engine than the auto.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

at those speeds the engine is screaming... you know whats slower than a 240D auto. a 240TD auto...

Personally, I don't like to sustain much over 75 in a 240D. They will go faster, but the gear ratio is pretty low. At 80 mph, they will be close to 4000 rpm.

is it possible to install a 2.47 diff on a 240?

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'85 300D Turbo - CA Version

Sure, just move the drivetrain to a go-kart and it can then get itself up to nearly 100 mph..............

An auto 240D with the A/C on can peg the speedometer.

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1976 BMW 2002- 100k
1995 BMW 325i 175k
1984 Mercedes Benz 300D Turbo Diesel- 270,000 mi

1981 Mercedes Benz 240D- Estimated 300,000+ mi Returned to the earth

I suppose it's physically possible, but I doubt it would be able to maintain highway speeds on anything except level ground. Even a 3.07 or a 2.88 would probably be too high. We're talking about less than 70 HP in a 3500 pound car.