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I just bought a 82 300 SD TD with 177K on it. It runs great, though the rear end was replaced by the previous owner, and the speedometer is off by 10 mph when at 70 mph. When driving at 70 mph, the engine rpm is at 3000. I was told by the owner that the mechanic put a rear end in from a gas MB, and that has caused this change. Could somebody on this forum confirm what RPM they get at 70 mph with their 82 diesel, as well as what the redline of this engine is? I want to get to the bottom of this problem, replacing the differential if need be, or putting larger tires on it. Thanks so much! -Jonas
 

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Engine RPMs while driving 70 mph

Even though it is posted that I'm going 70 mph on the speedo, I'm actually only doing 60. So in actuality, I'm running about 3000 RPM when driving 60 mph. Thanks.
 

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rpm @ 70

there is a couple of ways to correct this, ask the old owner which model that diff came out of. and get the speedo head for that model, or if crawl under the car and look at the diff on the right d=side there should be a tab or flat spot where the ratio is stamped, then contact your dealer and ask them who in your area do they send speedo's to. then tell the speedo the rear axle ratio
and see if they can recalibrate the speedo,
 

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Thanks

OK, this is helpful. I do have the original receipt for the work that was done, but it doesn't specify where the rear diff came from. I'm working with the mechanic that did the work, but it has been two years, and he isn't sure what happened. I also have a good rapport with the original one-time owner of this car, so that is helpful. This is my first Benz, and I'm loving it. Just want to get it dialed in, and get the best mileage possible. If I have to argue with the mechanic, I'm still curious what others are getting RPM wise at various speeds, as this would be concrete. Thanks! -Jonas
 

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part number for differential

I checked the differential, and the part number on it is 115 351 32 08. Any idea on where I could look this part number up to see which Benz it came from? The mechanic is giving me the run around, and I just want to see how far off the gear ratios are. Suppose I could call a dealership, though I'ld like to look it up online. Thanks much. -Jonas
 

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Part Number Difference

So my 1982 300SD Turbodiesel is suppose to have a differential of the part number 116 350 83 20. The one that is on it is a 115 351 32 08. Any idea on how I can find the gear ratios on both these differentials? I'll look on the bottom of the differential again, as this is what was relayed to my be the dealer. Just don't recall seeing this when I got the part number. I've got the manuals too, so maybe this will spell it out. Any help would be appreciated. I would think that the ratio might be encoded into the part number somehow. Thanks, Jonas
 

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On my 83 300d I run 3000 at about 70-75mph (so says the speedometer). Before I purchased the car I called a mechanic and he said this was normal but Im also curious to see what everyone else is running.
 
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