I talked to Eaton today and they actually laughed when I told him the make and model car, well, more like chuckled.

I really need to get a diff and tear it apart to see what I would have to work with. I can't imagine the ring gear is larger than 7 inches and the carrier has got to be very narrow.

Just doing a quick materials cost to machine up a custom carrier and purchase a locking mechanism it is at $1,200.00. P20 is quite expensive so I am hoping that the carrier is much smaller that I am thinking, (less material).

The other option is to design a locking mechanism that will work with the Benz carrier. Until I get one to look at I'm just spinning my wheels thinking of ways to approach the task, if it is a go that is.

Either way, unless it turns out to be a minor massage to fit an off the shelf locking whatever, in the 123 diff, the cost will be at least $1,200.00 to do it.

Still interested?

If you’re willing to spend 1200 dollars for a custom limited slip or traction lock differential, you might want to consider a custom use of a Ford 8.8 differential center section. I’ve been thinking about this, but have not acquired the parts to do a proper mockup and fit.

The Ford 8.8 is easily obtainable in a variety of gearing selections - 2.73, 3.08 (1981-1984 300D turbo's came with a 3.07, a Ford 3.08 would be a good fit), 3.27, 3.31, 3.55, 3.73, 4.11, 4.10, 4.30 and etc. It can be easily found with a factory LSD carrier in a junk yard or use aftermarket traction lock carriers that you can get anywhere.

The Ford 8.8 came in a variety of Independent Rear Suspension (IRS) vehicles.

Cars
1989-1997 Ford Thunderbird/Mercury Cougar – Cast Iron case
1993-1998 Lincoln Mark VIII - Aluminum case
1999-2004 Cobra Mustang - Aluminum case

Cobra/Mark VIII center section





Trucks
2002-2010 Ford Explorer - Cast iron
2003-2010 Ford Expedition – Cast iron

2003 Expedition center section



For the factory car center section, the cast iron pumpkin is the stronger compared to the aluminum pumpkin, but the aluminum is the lightest. For the strongest mounting, the early 2000’s Ford Expeditions are the best. They have a direct side bolt on mounting (as opposed to rubber dampening mounting) and in combination with the Thunderbird/Mark VII/Cobra rear cover, may work well on the modified Mercedes.




To make it work, obviously you would have to fabricate a mounting system that will fit the w123 subframe.

Mustang Cobra IRS





I think this can be accomplished using the four Mercedes differential mounting points on the subframe and custom brackets.
Although I am not sure of the length of the 8.8, if it happens to be the same as the Mercedes differential and can utilize the stock length driveshaft, the 8.8 pinion flange could be easily redrilled to accept a Mercedes style flex disk. But then again the case length probably doesn’t matter, if it is longer or shorter, the axles CV joints should allow for the diff to be positioned forward or back.


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1983 123.133 California
- GreaseCar Veg System

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Speaking of the axles, you would need to custom combine the 8.8 inner axle stub and Mercedes outer hub stub.

8.8 axles




Inner axle stub



Visually, Ford 8.8 appears to be a bit wider in between the axles than the Mercedes pumpkin.

Thunderbird assembly


The axle shafts, depending on which one you will use, might need to be shortened for use on a w123. W126 bodies may be able to use the shorter w115/w123 axle shaft to make it work. (but as I stated above with the differential positioning, the longer shaft might be needed to work on a non-90 degree layout.)

If stock Annular axles are the correct length, then maybe using modified axle flanges from the front F150 8.8 differential can be made to bolt with the Mercedes Annular axles.

F150/Expedition front axle flange




This might be a sacrilege to put a Ford product in a Mercedes to some, but it is a possible solution to the Mercedes LSD dilemma; hopefully it will give you some ideas.




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1983 123.133 California
- GreaseCar Veg System

DeliveryValve, you put a lot of work into that post!! Excellent information that I am sure others will appreciate as well.

If the Superturbos start braking rear ends, the Ford units may be the ticket. It would take some work to blend the manufacturers, but when done it would be pretty tuff.

One major requirement for this gentleman is to maintain serviceability, which means standard parts, (axels mainly), not necessarily MB parts, but non modified parts so they can be replaced when on the road.

So far it looks like the best plan of attack for him is to research the different models with the small ring gear and find a part number for a LSD.

He needs to replace an axel, so he was thinking that would be the time to swap the diff. He was hoping to be able to do the job for less than $1200.00, but regardless of the path, that is not realistic.

All in all, there is some good information in this thread that will hopefully benefit some members.

I'll post anything that gets done, if it gets done that is.

The 8.8 is a very strong differential. Strong as the GM 12 bolt (which is basically a carbon copy) and close to the Ford 9 inch.

As far as serviceability as I stated above, if you can make axle flanges that can mate to Mercedes style annular axles, then you basically can use off the shelf parts.

Annular Axle



Your best bet if you want use the same housing and gear ratio, is to get a 190 16v LSD carrier and do exactly that Tom did. But the issue is your mostly likely are going to have to renew the clutches and Mercedes clutches are expensive. Something like way north of $500.00. Where else the 8.8 clutches can be had very cheap. But it can be done and you will still have off the shelf parts with nothing to fabricate.


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1983 123.133 California
- GreaseCar Veg System