Nathan,

I wrote about it on the W140 Benzworld forum, yet it has worked fine on V12 and V8 engines. I have never done it on a I6, and cannot say how many pinion gears W140 M104 722.6 equipped cars uses? As the M112(V6) use three,the V8/V12 use four, so in my book it is a matter of comparing the front and rear replacements shafts in the transmission of your car to the different flavors of the W220 or the +2000 W210, and again I do not know how many pinions it has(I6 722.6 cars).

I used at minimum the rebuild kits from many suppliers, and they work well. They are around $200, but the ideal is to use Borg Warner machined frictions or Mercedes frictions not the stamped frictions in the kits. You will need a new Bonded front piston, two new updated sprags.I use CVC torque converters as they use Sonnax parts in them.

The wisest thing is to get the re-builders manual on the 722.6, and look at some YouTubes.

New revised 722.6 service manual - get it while can - Mercedes-Benz Forum

You want to replace all the seals...

Martin