rear differential gears
 

alright I have tried searching but to little avail. I really want to aquire a new rear differential with 3.46 or 3.96 gears if at all possible. 1985 300d with 340k. Anybody know what would be the most economical way of doing this. Is there a company that reproduces mercedes gears? where could I get the ideal differential? I am not against simply buying a used differential and regearing it, just a little lost being new to this particular community :)

346 gears are around as they came on the 300D NA. I have some but might use them so they are not for sale. 3.90 was offered on the 220D and may bolt up to a 123 diff. The 369 was offered in the 240D and is very common. I may have one of those. I'd be happy to sell if so....if that would be of interest to you.

What is your purpose in wanting such low gears in a 300D?

You do know the 85 has the 2:88 Differential. that was the highest gear ratio available.

A 3:46 and a 3:96 would be a lower gear ratio. good off the line performance, but the engine would running at a much higher rpm at hwy speeds.

Which way are you trying to go?

Why regear your existing Diff when you can just swap in a Diif with the ratio you are looking for.

Charlie

pulling
 

It sounds like the OP is either sled pulling or trailer pulling on the farm. Obviously, the OP is not planning on driving on the interestate.

IF you do swap out your rearend, I'm probably interested in obtaining yours if it's in good condition.

Yes I have a 369 out of my 240D. It is a real stump puller, could also be used for plowing corn if the soil isn't to heavy. And it is for sale cheap. PM me!

I'm totally up for swapping either a 3.46 or a 3.69 diff for your stock 2.88.
I'll even swap the instrument cluster for yours as well.

Is there a list of the diffs by year or model anywhere?

What vsteck said. You change the rear end you have to change the speedometer head or cluster if you want any fairly true mph indication. Most members just change out the whole rear pumpkin rather than internal gears.

Wouldn`t make any sense to swap the gears and then have to set up the gears, spacers and bushings etc.... plenty of Differentials around to just swap the whole thing. Haven`t read of anyone just swapping the Ring and Pinion.


Here is a list of the chassis and differentials that were used together.

Diff info?


Charlie

116 body SD- 3.07
126 body SD up to 84 - 3.07
123 body wagon from 81-84 3.07
123 wagon from 77 to 80 3.46
123 body sedan/coupe 300 from 77-81 3.46
123 body sdean/coupe 300 from 82-84 3.07
123 body 240D all years, and transmissions 3.69

123/126 300XX 1985 2.88

gassers have all kinds of crazy ratio's from 2.24 or so and up.

all the pumpkins from the above years are interchangeable physically.

No difference between turbo and non-turbo sedans? Worth the work to trade out a 3.46 for a 3.07?

123 turbo started in 81 for the wagon, and 82 for the sedan and coupe my list notes that change...
non turbo is 3.46 turbo up to 84 is 3.07 85 is 2.88

Oh, I see. I didn't know if the turbo and non turbo models were sold side by side. I suppose my parts car has the 3.07. I'd like to squeeze a few more highway miles out of the wagon, just don't want to be defeated by every hill.

only the euro vehicles were available non turbo side by side years...
all US models are the same. 123 77-80 are non turbo wagon got turbo in 81, and all the other model 300 123 bodies got turbo in 82
the 240 never got the turbo.

Learn something everyday. haha.

If you have a us spec car it is then a turbo and for better economy you can swap with minor mods to a 247 diff from a 380
SE. You will give up some acceleration on take off but will work pretty well on the highway.

Even with 2.88's a properly running 617 turbo shouldn't have problems with hills. If you're having problems on hills, you have another issue-fuel supply issue, ALDA plumbing, fuel supply issue, soft wastegate spring, fuel supply issue, improperly tuned automatic transmission, fuel supply issue, etc.

I have an NA 300D with a 3.46. I'm not the OP, I was thread-jacking. I don't really have problems with hills now really, have to just be going pretty quick at the bottom to maintain speed at the top I was just wondering how much worse hill climbs might be with a 3.07. I live in the mountains, everything is a hill.

I built up a car using a euro 300D and a 307 diff. Taking off on an incline was a little dicey but once moving I never had an issue. I don't mind shifting down for hills though and some seem to resent it. With a four speed and it all in an 83 240D body it got 30 mpg with regularity.

Well, you might just have to be a little quicker at the bottom for a run up the hills going to a 3:07. looks like a 11.28% difference between a 3:46 and a 3:07 Diff.

Charlie

alright sounds like the 3.96 may be too much then... so perhaps the 3.46, does anyone know what rpm I would be running at 75mph? this is not my daily car but I would like to have a little better off the line especially with the larger off road tires I am putting on it.

I can have someone look at it and tell me how it looks. I have a good mechanic that does my work here and could tell me. How far are you from Baltimore?

That would depend on the tire size you're using.

(0.00595) * (RPM * r) / (R1 * R2) = vehicle speed in miles/hour

where:
RPM = engine speed, in revolutions/minute
r = loaded tire radius (wheel center to pavement), in inches
R1 = transmission gear ratio
R2 = rear axle ratio

linky: http://wahiduddin.net/calc/calc_speed_rpm.htm

The transmission ratio is 1:1 in fourth gear. What are planning on doing with this car?

I'm with skippy on this. These engines have good power for climbing hills with the stock gearing. If you put gears in that will raise engine rpm you will really ruin the fuel economy. the engine is an air pump. If you raise the cruising rpm 20% you will raise the fuel burned commensurately....I mean close to 20%, so if you go from the stock 288 gears to 346 gears that is increasing the highway rpm by about 15%. So if you are getting 25 highway mpg now that will drop to about 20.

Its nothing I would ever do.

It depends on the intended use. If the OP is going drag racing or mud bogging, deep gears may be a good choice.

If he goes mudding in an '85 300D, I want pictures. :P

and my intention with the car is to cover it completely in duct tape, put a loud exhaust on it, very large tires, low gearing, strip the interior and replace with racing seats, and lots of other weird things... then eventually start doing something new and unique to my 300cd...

Seriously?

well ya... I bought the wheels and tires today, have racing seats from my bronco, the exhaust seems like a pretty easy thing, the only tough things seems to be the rear differential and I want to add a third tank in the trunk as I need more range. Check out my sweet duck tape job though, just search for my other posts.

WOW just WOW!!!

I guess you will need three full tanks in the car if you are going to much much lower grearing.

Duct Tape? Really? HMMMMMM now how old are you? 16???

I really don`t follow this...................oh well.


Charlie

Well I always wanted to cover a car in duct tape... And seeing as this car was only $450 I couldn't see spending more than that on a paint job...

I got my 1980 240D for free from the original owner, with 306K, so with that thinking, we shouldn`t put any money into it.

Iam sure we are well over $2000 by now.:)


Charlie

Well, if it's a cheapie, I guess I understand. I've wanted to more or less cover a car in political type bumper stickers, but I keep buying vehicles I have too much respect for. The closest I got was a Ron Paul sticker on the back window of my 240D. My 300D and my Kawi don't have anything like that on them. One time I saw a Yugo for sale for an asking price of $500. Maybe I should have gone for it.

I always wanted to brush paint a car. I did the repaired area on the 240 I built from a wreck for my first driving child .

I have a 3.07 under my 300 TD (NA) and what a relieve it is. The wheels are 195 65 15. And the speedo is dead on. Just sweet.

I live in the mountains too. The longest hills, with load, I have to take at 8o km/h -50mph. If not I gear back to third. On a side note; I am looking forward to getting the turbodiesel motor in, since I am shying away from using my trailer.

I started out with a 3.92, if I recall correctly. (The car was a 200 T) Quite hysterical at 80km/h.
Then I had a 3.69 from a 300TD NA. That was better, but I couldn´t accept the high rpm´s, even tough I am living in a country where the speed limit is mostly 80km/h-50mph (!) ( a freeway, what is that?!:))

I still have trouble picturing the odd german grinding away at 120-140km/h 75-90mph on the autobahn with that standard 3.69...

I don't. I used to do it all the time in my 240D. Lots of times I would just floor it and leave it there until it was time to slow down or until my leg started cramping.

LOL