Is this a do-able swap? I have a donner car which is a '85 380SE. The reciepient will be a '82 300SD.
Does the diesel have enough torque or will it lug? MPG?
I do alot of flat hwy driving and thought the SD may benefit by running a little less rpm.

Also, It seems like the average mpg for the 80-85SD is around 24-28. I always wondered why they aren't any better than this. I have a '92 dodge dually getting 23.7mpg. Its got a plenty of power and lugs around alot more weight, wind and rolling resistance.
Same fuel so, what makes one much more effiecient than the other?

What ratio is stamped into the housing?

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

WhiskeyDan,

If the donor rearend is a 2.47, stop doing whatever you are doing and install it into your 300SD. The change is phenomenal. I did mine about 2 months or so ago and would never think of going back to a 3.07. (I am guessing that you have a 1981-1984 300SD). MUCH quieter at highway speeds with no apparent loss in acceleration. It is not a difficult swap and the benefits are outstanding. I have not gone on a long trip yet, but commuting MPG is right at 30.

Tom

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1993 300TE
1984 300D
1984 300SD
1976 BMW R90S

Could you post your 0-62 mph acceleration time? I see BIG differences in my 190Ds using 3.23 and 3.42 rears and would expect the change from 3.07 to 2.47 to be MUCH worse, but I'm willing to be convinced if you could provide some data.

Marshall

Marshall

Well Marshall, you inspired me. Tonight I took my 84 SD out for a stroll. The car has a full tank of fuel, 2 people on board and 212,000 miles on the engine. The ALDA is still factory sealed. Level road. Ambient temperature of 78 degrees F. I did four runs 0-60 and averaged 14.8 seconds. I don't have a baseline to compare, since I did not do any 0-60 runs with the 3.07. I think this is a pretty respectable time. What do you think?

Tom

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1993 300TE
1984 300D
1984 300SD
1976 BMW R90S

according to the mercedes benz buyers giude a '79 sd does it in 13.0. i suspect that an 84 would do it a tad quicker since i think they are a little lighter. not sure of the rear end ratios in those two. are they the same?

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[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.

Mercedes lists 0-62.4 mph acceleration time as 15.2 sec so you're right there. That's VERY surprising to me as my naturally aspirated 190Ds are very sensitive to rear end ratio/tire size. I'm surprised that yopur turbo isn't, but your numbers suggest the switch is very reasonable. Mercedes did use a 2.88 in '85 so maybe the 3.07 really was a poor choice. Please us know if you're still pleased after the novelty wears off and if you're able to maintain 30+ mpg highway mileage!

Marshall