Greetings:

My 1982 300D differential has a lot of slop and whines a bit. You can freely turn the driveshaft input through 60 degrees of rotation without moving the axles. That's a lot! It makes for a rough transition between "power on" and "power off" for example.

I have an opportunity to get a low-mileage 1985 300TD differential at an acceptable price.

Will this fit into my 1982 300D sedan?

Hopefully someone has enough "swap" experience to let me know.

Thanks,

Ken300D

Should fit easily in the back seat or the trunk. Sorry--couldn't resist!

One thing to consider is that I believe the gear ratios are different in the TD versus the sedan. I think someone mentioned that on a thread a few weeks ago. I think the TD has a lower gear ratio so you will give up a little acceleration for a higher top end.
I can't remember if an 82300d is turbocharged but that change in gear ratios could have a detrimental effect on the pick-up of a non-turbo.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

as far as my memory works, the non-turbo 123 300 diesel cars generally have 3.47 to 1 final drive ratioes, whereas the turboes up to 1984 have 3.07 to 1 and some, perhaps not all, of the '85 model turboes have 2.88 to one, which would really make a non-turbo slow off the line, but might put you in competition for fuel mileage figures with the various VW rabbit diesels. You would also need to swap speedometer drive gears, or at least put some white-out marks on your speedo.

On the other hand, under my present driving circumstances, I'd love to find a good 3.47 for my '85 300TD.

I'm aware of the ratio change, and actually happy about it. I would not mind lowering the engine revs a little bit at interstate cruising speed.

It's just a matter of confirming from someone who knows if the wagon differentials fit properly in the sedans.

Ken300D

One source for used differentials is PGAuto in Frederick, Maryland. My source is going to UPS a differential from a low-mileage wagon.

Still hoping someone this evening knows if the wagon and sedan use the same differential.........

I guess there's not that much differential swapping required, especially if you keep up with the gear oil renewal schedule. At 325K miles, perhaps mine has been ignored most of the car's life. So getting a low-mileage one will be nice.

Ken300D

Thanks, I really appreciate the help. I have a differential coming from someone that I've dealt with in the past on EBay. If there is any kind of problem with it I might get back in touch with you for your '85 gearbox.

I do a lot of empty sedan interstate cruising, so the change in ratio is exactly what I'm looking for to reduce the engine revs. Besides the differential gear ratio change, I've also changed to 15" MB wheels from a later 300SE - so there could easily be some offset for the speedometer. Rather than recalibrate, I plan to just develop a mental offset chart using the police "radar speed reporters" that get set up all the time around here. (Actually there was little change in going from 14" to 15" wheels.)

So I'm looking forward to yet another incremental improvement in the car. I don't know why this always happens, but I always end up doing major car work (major for me anyway) in the middle of WINTER !!!

Guess it will be time to do those rubber differential mounts too.

Again, thanks for the input.

Ken300D

Stock tire size should be 195/70-14. 205/65-15's are 3% larger, so at 60mph on the speedo you are going 61.8mph. I would love to lower the cruise rpms as well. The diff swap would appear to be easy. How hard is it to change the gear in the trans for the speedo drive? Thanks, RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

The seller kept changing the terms of delivery, so I decided to cancel the deal. I can probably do better in person at PGAuto in Frederick MD.

I'm running 195/65-15 on the 1982 300D. This happens to be the same as the recommended stock size on the 1987 300D that I also have, so I am running the same tires on both. Sears sells the Michelin Weatherwise tire at a good price. It's not H-rated, but I have the personal opinion that H tires are not needed on either car for the way I drive. Thus, I get tires that last twice as long at half the price. The only drawback is that I have to take the loose wheels in to Sears and refuse to tell them what car its for - because they won't put anything but H-rated tires on the car.

I really enjoy having a 60,000 mile tire when everyone else gets a 30,000 mile tire at twice the cost!

Ken300D

Othe r than the ratio difference, they are the same. Chris

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

Ken300D,

You don't need to recalibrate the speed, just get the speed gauge from a car that has the same rear end ratio. That automatically recalibrates the speed as both the rear end and gauge are from the same set up.

Eventually, you might want to go to the 3.47 and put a later model 5 speed in the car that way you get the accleration and the lower rpm cruise that you're looking for. Just expect it to take a long time to fine one of the euor 5 speeds. Get the one thatr has a one piece transmssion case and bell housing. (Later model.)

Finally found one myself and will be putting it in the "Super Diesel" next month after my move to Nevada. Can't wait!!

I'll post results once we're done.

Ben

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www.reproduce100s.com

I like the idea of taller gears for certain cars, especially turbocharged cars that have a fairly flat torque curve. With some cars, taller gearing actually makes the car faster overall... less time is lost by shifting, and the engine is able to stay within its powerband for longer periods of time.