Yes, it was originally sold in a sunny lower state so ASR was not needed. Given you are in a northern state where snow is possible, most cars probably had ASR.

I'm pretty confidant that all of the rear ratio magic occurs in the ABS controller but have not verified this. I don't recall if I built a harness to test modules off the car and look at version coding. ( I made a harness to access everything else. )

If TCM version coding is the same between 3 and 4 channel ABS, then the ABS / ASR module performs the magic. The ABS / ASR module is definitely different between the 3 and 4 channel.

There are 2 chips in the ABS / ASR that look interesting ( From a 97 SL500 , probably same as 320 and 600 ) There is only one crystal so the 2nd one might be some sort of interface.

1st chip
Intel AN87C196CA L6400890A CR 1986 / 1993 ( 68 pin )
( 8XC196Lx family ) Microcontroller

Similar to AN87C196 pdf, AN87C196 description, AN87C196 datasheets, AN87C196 view ::: ALLDATASHEET :::

The non " CA " version has 24 K one time PROM and 52 pins, the " CA " on the board has 68 and seems to be the automotive version.

Rochester Electronics ( a company that remakes / has tons of obsolete stock, at a price. ) shows a 68 pin " KC " version targeted to the automotive market. AN87C196KC datasheet(4/26 Pages) ROCHESTER | POWERFUL MICROCONTROLLER for use in the automotive market

If the ABS module has version coding, there has to be another non volatile memory somewhere.

2nd chip
Intel B58477 < Bosch house number L6393586 BB34002 CR 1986 / 1991

You are still on topic, researching the 722.6 controller is the goal.

At least up to 99, the 722.6 case was cast but not drilled for the rear sensor. If the G wagon has a 2 speed transfer case, speed from trans tail shaft is a must.

Did any of the ML cars have 2 speed transfer?

For an add on external drive shaft mounted sensor trigger wheel, I'd use a chain sprocket with the tips of teeth ground to give more dwell time at top of sine wave.

Also, here is a power flow through the 722.6 https://www.youtube.com/watch?v=zQwN2-9mLME

That's about the only thing I miss from working day to day in the car repair business. Being able to create a mental inventory of off the shelf parts really helps when making something custom.

I got out of day to day in the late 90's and went into industrial machinery repair / product - machine engineering. This is far easier than working in the automotive world even though businesses think industrial is more complex.

No the coding is different in the tcm for sure. I promise you that the TCM reads both rear wheel speeds in a 2 wheel drive car and all 4 in 4matic cars. Hi/low is handled by telling the tcm it is in low range and it knows the low range and then adds that into the calculation of the output shaft speed. This is not a guess.
So this special ABS sensor in the diff one has to have code to set that up. It is not accounting for gear ratio at all. Just pulse count.

I'm considering a similar swap .I have a 94 E320 w124 m104 in need of transmission , have the original 722.4 in process of rebuilding, and have recently acquired a 97 C280 w202 m104 runs good but not sure if I want to pay 2 years back reg. and penalties , go thru smog and restoring the trashed interior so was considering using it as a donor and putting the 722.6 in the 94 E, could pull whole power and drivetrain , rear diff. and control mods but think the 2.8 would be disappointing as it has considerably less power . would the engine control module from the C 280 work with the 3.2l or the transmission control from the C be compatible with the engine control from the E . either way there is a lot of wiring harness swaps involved . any thoughts or suggestions ?

Lothar,
I am in a similar situation with a slipping 94 E320 transmission. There are at least 4 paths to choose from.
1) rebuild existing transmission. The most sensible choice
2) install a 6 speed manual transmission. I believe you want one from a 4 cylinder car like slk230 to mate with M104. The 6 speed has a low (high numerical) first gear which is a good match for the 1994 2.65 rear differential.
3a) install the C280 driveline. Engine, 722.6 transmission and 3.07 rear axle. Changing the axle ratio will improve acceleration so the 2.8 engine may be fine.
3b) like 3a but use the 3.2 engine with the necessary parts from the 2.8
4) 5speed manual transmission.. All parts w124 series so minimal or no fabrication. 3.07 differential probably best
I'm thinking of 2) or 3) for my 94 wagon using a 97 E320 as a donor. My existing transmission only slips occasionally so repair is not urgent for me. Let me know what you choose

Thanks to everyone in this thread for all the OEM vs aftermarket discussion. It's been a great help to me