400E Upgrade - Rear Differential - Wow!

[Mike400E]

With much anxiety I bought a 2.82 rear dif and lowering springs (See a different post for that upgrade.) from Carl at BergWerks. The rear dif was $1295 (Non ASR.), the speedo gear was $150, freight was about $85, and labor ended up at $350. So total cost was about $1900.

I can't imagine another upgrade that would make so much difference! The original rear dif was not well matched to the motor's powerband, which is rather peaky. Good power starts at about 3000rpm, and gets really strong at 4000rpm. While the original rear dif made for economical highway cruising (27MPG!) it made the car very sluggish off the line. And when cruising around town, sometimes two downshifts were required to get the motor in the powerband. And there were other times when the tranny was close to a shift but would decide not to, so even with 275HP on tap, acceleration could be wimpy. With the original rear dif a strong 4-3 downshift on the highway occurred at about 75MPH.

The new rear dif provides for much quicker starts from a standstill, and allows the motor to stay closer to it's powerband all the time. The 4-3 downshift now happens at about 55-60MPH, and it is a much stronger push than before. The car feels much more lively all the time, and is much better matched to the motor's power characteristics.

Carl estimated that the 0-60 time would come down about .5 - .6 seconds, and I definitely believe it! The entire nature of the car has changed from a rather sedate family sedan with a decent high end rush to a very strong V8 with lots of go on tap all the time. Mileage does not appear to have suffered too much. Whereas I used to average about 22MPG in combined city and highway, I am at about 20MPG. (And I am definitely not being gentle driving around!)

In short this is an incredible upgrade for the money! I can't imagine a supercharger, turbo, NOS or any other upgrade providing as much bang for the buck as the rear dif swap. If you have stock 15" X 195 tires, you may over whelm them, however. I have 16", 205's, and I think they help keep the motor from spinning the rears too easily.

Please email or post if you have any questions!

Thanks -

[Holson Adi]

Did you install everything yourself? If not, how many hours did your mechanic charge you?

The speedo gear took care of the speedometer discrepancy, yeah?

This would be an awesome upgrade but I would need an ASR diff.

Congratulations BTW!

[Mike400E]

I definitely didn't do my own labor! Al's ******** is a Denver area, Benz only shop I have gone to for many years. He did the rear dif in 3 hours @ $90/hr, and sent the speedo out for the gear change.

An ASR dif is actually LESS expensive - only $995, I think. The rear dif is a HEAVY piece, (About 85 lbs.) and would require some hydraulics to get in place.

[DslBnz]

The '97 E420's start out with 2.82 rear differentials. And, they have an overdrive gear for fuel economy. Sorry, I didn't mean to brag.... Wait, yes I did!

Some of you folks don't care for the W210 bodystyle, so I guess that might be the tradeoff for you.

[wjm]

Holson,

Where did you get the chrome shift surround?

Willy

[gsxr]

That's way cool. Is your new diff limited slip, or standard (open)? I'd think you'd be lighting up the right rear most of the time. That's interesting about the speedo, I thought you'd replace the drive gear in the transmission, not change the speedometer gearing. But, whatever works & is accurate, I guess!

On a related note. Has anyone looked into stuffing the later 5-speed automatic into a W124 chassis? That would allow an even lower rear end, like a 3.07 or 3.27. Here's a PDF with the gear ratios for the 4-sp and 5-sp trannies:

http://www.meimann.com/docs/mercedes/Tranny_ratios.pdf

[Mike400E]

Mine is a standard, non-ASR. The ASR dif is actually cheaper from BergWerks.

I understand he can get a 3.06. I wouldn't consider anything higher unless you were planning to only race. The 2.82 turns about 3000RPM at 75MPH, which is pretty fast compared to about 2200RPM with the original. My mileage on the 2nd tank is still about 20MPG.

As far as burning the tires, I do have 205/16's rather than the 195/15's which were stock, so I think that helps.

Mike

[gsxr]

The stock tires were woefully undersized, IMO, and the Euro models came with larger wheels & tires (IIRC). I'd say a 205/55/16 on a 16x7 wheel is the minimum, and if you could bump up to a 7.5 wheel with 215 width that would be even better. Stock 16" and 17" wheels (7.0-8.0 width) from the W210, 208, 203, and 202 chassis mostly bolt up with no clearance issues... might help with that wheelspin "problem" you now have...

[delsman]

Sounds like a terrific upgrade. I've been excited about it since you posted a week ago. Driving and imagining how it would change things.
However one of my concerns is wear and longevity. You mention the engine spins 800 rpm faster at 75mph, that is a pretty large jump up. Does anyone have a feel for how much increased wear would result with this. Would it be bad at very high speeds? Sometimes I like to race airplanes Further I have a feeling that the trans would be put through more torture? Very exciting mod however.

[Mike400E]

Actually, I checked it out very carefully today and I turn 2900 RPM at 75MPH. This is still lots faster than before. The good news is that you are very close to the engines powerband, and if you punch it and kick down from 4th to 3rd, you spin about 4500RPM. Yikes! You are right in the meat of the powerband, and 90-100 comes up VERY quickly indeed. Faster than any other car I have ever driven or owned. Making your way through city traffic on the highway is SO much easier than before!

The engine is SO smooth at revs that it really isn't ruffled at all around town on the highway. I have yet to drain a tank on a deserted stretch. I suspect it would lose some of it's relaxed gait in that situation. A tradeoff I am definitely willing to make!

[georgie]

I've been on the fence about the diff swap with my 400E, I finally decided to do it and found out that Bergwerks is out of business. I can find the donor diff from a 140, where can I find the speedo calibration box that Bergwerks used to sell?

[Mike400E]

Georgie:

Sorry man - I do not have the Bergwerks invoice any more, and the car was totalled last summer, so I can't even look at it! You might try some of the 'Benz shops around who could have a clue. There have GOT to be guys on this forum who can help, too!

Mike

[DangerMouse]

Originally Posted by georgie

I've been on the fence about the diff swap with my 400E, I finally decided to do it and found out that Bergwerks is out of business. I can find the donor diff from a 140, where can I find the speedo calibration box that Bergwerks used to sell?

Speedometer calibration box is an easy question to answer http://www.blackrobotics.com/

Convinced to swap in a 2.82 rear (with 16-inch wheels), but would like to find someone on the board who actually rebuilds them versus a recycled part in unknown condition. I have personal experience with "mildly used" differentials that were loud enough to wake the dead even with synthetic gear oil...

Does anyone know of an individual or shop who still builds 124 performance differentials?

Thanks!

[amg280]

Guys...

I did this about 2 years ago...at a total cost of around $700!!! Call around salvage yards and locate a W140 4.2 119 (400SEL, 400SE, S420). It will most likely have ASR (mine had asr, which worked out well). I got mine for about 550. When you take the old one out, all you have to do is swap out the back plates, you will know what i mean when the time comes. I swapped the diff's out in under 2 hours myself, in my garage. Its not that hard.

Regarding the speedo calibration, dont touch the instrument cluster. You dont need to change any gears out. The speedo is electronic. There is no cable. It uses an electronic pickup on the tranny. Buy this:

http://www.abbott-tach.com/era.htm

Its about $125. It converts it electonically. Its easy to hook up (behind radio) and works perfect. And if you ever switch back, simply uninstall it. You can also run custom tire sizes and dial in the correct ratio to make the speedo accurate.

Let me know if you have any questions...

[mcbear300E]

Regarding the ERA patch box, does that box work with a W126? I am getting ready to install a set of twin turbos in my 300SEL and will be changing out the 3.46 diff so I can keep tires on the car over a week.

My initial thought was to just get a diff from a 560SEL and do a direct replace since it has 2.47 and the twin turbos will more than take up the lag w/300 hp on deck. The 2.47 will also let me cruise at highway speeds at less than 3500-4000rpm which gives only 22mpg.

Does this make sense?