rear differential replacement options
 

I'm looking for some rear differential options for my US spec. 380SE. What is there out there available that would give the car a bit more oomph..

There are two different differential cases on the W126 cars.

The 5 & 6 cylinder cars use use a 1 liter capacity case, the V-8 cars use a 1.3.

Not sure what was used on the 380SE, but the diff for your car was used on the W116 and R107 chassis as well.

I think the lowest (numeric) ratio is 3.07 found in the 450 series of both the W116 and R107. Late V-8s used a 2.47 diff.

Ratios down to 3.69 can be found in the 1 liter case, generally used for the M110 engined cars, but this diff may not be robust enough for even a M116's torque....

Jim

SO I attest the 3.07 would be what I would be looking for? I was made aware that the 86' and up had a deffenret mounting due to the heatsink fins ergo I would need something from 85 down (Gen 1).

A 3.07 from a 300SD would surely make it quicker, but it would run at higher rev's and use more gas.....and more engine wear.

What would be the next step from the 3.07 since I don't want to rev like my non MB's on the highway. I just want this to keep up somehow with my euro 380SE. obviously there is a big performance differance but I figure with the rear needing to be replaced and the center support bearing on it's way out.. I'd do it together and kill 2 birds with 1 stone.

1985 SD's had a 2.88. That'd be your next option.

That said, I'm going to a 3.07 from a 2.24 for my 500SEC.

I cant speak for the 126 series but for the 107, in 86 when the 560 came out they went to a bigger rear which forced them to move the mounting. However in the later 107's the old mounting holes are still in place in the chassi. You just need to remove the rubber plugs and put in the threaded insert plate. I believe this may because the 107 was available with a 6 cyl in Europe and probably used the smaller diff. So the 1986+ 107 is backyards compatible but I don't know if the older ones would be forward compatible. I would suspect the 126 may be the same situation.

Unfortunatly not. The subframe unit itself was changed from gen1 to gen2, and diffs wont interchange without a whole lot of modification as I found out. I originally thought all I had to do was swap the rear cover plate, but after getting a 2.47 gen2 rear end, I found it wouldn't work.

I am moving up to the 2.65 diff.
 

I am going from the factory 2.47 on my '91 560SEC to a 2.65 because I'd like more grunt from the lower end, and don't mind scrubbing a bit off the 152 mph I once saw on my car as it is now.

The vintage AMG Gen II catalogue, on its differential options page describes the available ones as going from the "mild" 2.65 all the way to the "neck-snapping" 3.46, (with the other available AMG diff ratios being 2.82,3.07 and 3.26)

There for the 2.88 would be a better option combining the acceleration as well as the highway, well I understand it'll be a bit lower but I have only taken the 380 to 110mph so far. In your opinions, would you choose the 2.88 or the 3.07?

If you're driving the car a lot, I'd probably go with the 2.88

I'm opting for the 3.07 because my car sees a lot of autocross and track events.

I'll keep an eye out for the 2.88 or the 3.07. I don't drive her much at all. She sleeps side by side with the import 380SE and 500E. Thank god they are all black...

mines already off with a US speedo in a euro car, who cares? I just use a GPS for a speedo now.

not always. my 83 has flanged axles.

why would you need to change the subframe if youre using the 3.46 housing with the 560LS? it'll be the same as whats in your 84 now.

I put the 3.07LS from a 1973 450SE in my car last night. Everything worked perfectly. Thanks to Pooka on here for saving it for all these years ;)

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Am I correct to assume then that the 3.07 from an 84 300SD will bolt right up to my 85 380SE with no problems? Besides doing the mount, center support and bearing and flex discs, Is there anything else?

Someone said that the axles will need to be swapped if using a diesel diff, I'm not sure of that so let me know what you find. I have an 81 300SD here I'm going to pull the diff on, but haven't gotten to it yet.

I'll grab the parts list but in the pictures you provided, what diff di you put into the W126 with the new rear diff mount cover?

It's the same cover from the 450SE, just really cleaned up. also identical to the one on my SEC originally, only diffence is inside, check my thread in the performance section for more pics.

Its going to take some getting used to, I keep waiting for it to shift into another gear sometimes. figure 3k RPM @ 70mph.

3.07 is what this car should have come with... plus a 5th gear in the trans to accomadate.

116 body, yes.

hmm. While great for takeoff, if you drive above 60mph the 3.46 is going to be wayyyy too much. You pretty much have the same setup I originally have right? euro 500?

I have the 3.46 here from the SLC we parted, I may stick that in the 380SEL at a later date but I wouldnt do it with the 500.

The differentials that AMG sold for the Gen II W126 ('86-'91 US cars)
 

Well I have just bought the 2.65 from Jonatham in Atlanta that he had.

I had thought for ordinary fast driving the 2.82 would be enough, but then again, the AMG 1987 catalogue states the diffs they sold at the time were the "modest" 2.65, the 2.82, 3.06, 3.27 and the "Neck-snapping" 3.46


My reckoning, without having done a dyno test yet, that my stock 2.47 ratio and totally stock engine, with AMG headers and exhaust, and the big Remus 2-in-2-out exhaust (guaranteed 2 hp on the dyno) has boosted the car's HP by 30 hp with no other mods done yet.

That puts it in Euro "kat" territory, the Euro gen. II Kat motor had about 272 hp..



Not into the incredible euro ECE engine, about 300 hp for those, but what I have is worthwhile.

Stepping on it hard from 90 mph is as smooth as pouring water, past 135 mph.

Absolutely great.

If it scrubs a few mph off the top end I don't care, as I had it up to 152 once and the accellerator wasn't even floored. A mere 4800 rpm or so was
spinning at 145 mph.

heh yeah Jim, I havent hit the top end limit yet, but with my old diff, It was 4,000RPM with the speedo showing 140, but the speedo used to read under the actual speed, it was probably closer to 160. damn it was loud!