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  #1  
Old 07-30-2005, 08:34 PM
Howard
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81 240D Manual 4 speed.

Would anyone care to guess the outcome (performance loss/fuel Mileage) of replacing the stock 240D differential carrier with one from a 300D?

Also: How/where is the rear ratio indicated/posted on the 240 & 300.

My 240D (running well) is only delivering 27 mpg at 60 mph.

I could stand a little loss of spunk if it would enhance mpg.

Thanks for your time.
Howard, North Carolina


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  #2  
Old 07-31-2005, 01:38 PM
t walgamuth's Avatar
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Join Date: Apr 2005
Location: Lafayette Indiana
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well

if it is stock the ration should be 3.69. there are diffs out there in 3.46, 3.54 3.27 3.08 and 2.88 i believe all will bolt into your car. personally i would not do it. the 240 is marginal already, but if you do go for the 3.54 or 3.46. then also get a speedo for that gear ratio so you will have a correct setup. your mileage will pretty much correspond with the numerical difference in the ratios. divide 3.69 by 3.54 and you will get about 3% then you will use about 3% less fuel.

tom w
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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.
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  #3  
Old 07-31-2005, 02:12 PM
Howard
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Thanks Tom:

Thanks for your input Tom.

What do you think is a stock ratio in a 80 300d station wagon?

American cars sometimes have a tag on the diff. Is there such a thing on MB.

Howard
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  #4  
Old 07-31-2005, 03:14 PM
t walgamuth's Avatar
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300td

if it is a non turbo and i think it is it should be 3.46 i believe.

tom w
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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.
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  #5  
Old 08-01-2005, 09:51 AM
LarryBible
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It is very simple to determine ratio of any axle by raising one rear wheel and counting turns of the driveshaft vs. turns of the wheel and multiply by two due to the spider gears.

Going to a higher gear on this underpowered car could result in worse fuel mileage depending on your driving style and conditions. It CERTAINLY would result in measuring acceleration with an hour glass.

You already have a 30MPG car. Assuming you increased the fuel efficiency by 5% (a pipe dream,) and assuming $2.25 per gallon diesel price you would save $3.57 every 1,000 miles in fuel cost. Does that warrant the hassle of finding a rear axle and matching speedometer and installing them plus the expense and worse yet can you REALLY afford to lose what little power this car has to offer?

If you are that hard up for fuel money, I think you need to rethink your entire situation.

Good luck,
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  #6  
Old 08-02-2005, 11:42 AM
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Try some higher profile tires first.. see how she likes it .
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  #7  
Old 08-02-2005, 11:48 AM
boneheaddoctor's Avatar
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The '83 300D turbodiesel has a 3.07 diff...but I question the 240D's ability to pull the car with the higher gears...its a real joy to get moving up a hill with the stock gears...
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  #8  
Old 08-04-2005, 07:49 AM
Howard
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Thanks Arthur:

Quote:
Originally Posted by Arthur Dalton
Try some higher profile tires first.. see how she likes it .
Just installed 195/r75.......so far so good. Wish I had opted for 205 now...

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