My W124030 with 170,000 miles developed a tranny fluid leak.
From the position it appeared to be the front pump seal.
After further look see, at my dealer, the fluid was coming from a large allen headed plug mid-way to the rear of the case.
This plug is the band strut retainer/alignment pin.
It has 2 o-rings in the bore aft of the threaded diameter where the plug screws in.
To unscrew the plug any major amount to seal in the bore risks the chance of the strut falling out of position and major disassemble of the tranny.
You might as well reseal and renew friction items while it is opened for these 2 little o-rings.
Pooh Pooh on that, my tranny is strong but has this oil leak.
What I need is a gasket to seal the flat surface where the plug seats against the case.
Light Bulb comes ON.
I have electrical rosin cored solder 0.030 inches in diameter.
Use it as a compression seal.
I go to my favorite independant for some non-traditional repair.
The plug was unscrewed just enough to allow the solder to slip in place. You must wrap the material in a clockwise direction to keep from expelling it as you tighten the plug.
Clean the area using throttle body cleaner, blow off and reclean.
Apply as much RTV as you can in the gap, then wrap the solder overlapping the ends.
Torque per spec.
Allow the RTV to cure.
It has been 1300 miles since my EL Cheapo repair and the old tranny is dry on the outside as when he was new.
The leak rate was 1 qt/300 miles; Big Time!
If you have a leak in this genral area, make certain from where it is coming before popping for front pump seal or disassemble for this plug leak.
Happy Trails beep Beep from Houston!!!
Donald, El Cheapo

Well, I hate to make comment on your repair. I hope you have long term success.

The only reason I am replying is that I would hate to see someone make a mess of something doing this when the proper fix is so simple.

The problem you were warned about is that the end pin that goes into the band cup is limp and normally hangs at about a 45 deg angle to horizontal. It won't enter the cup unless it is made to stay straight. A little heavy soluable grease does the trick quite well. You can not see any of this once the piston is installed but there is no way to have it go together wrong.

Worse case if the plastic pin retainer comes off is that the valve body will have to be dropped to hold the pin as the assy is threaded in. If we are servicing the tranny at the same time we often just do this as its also a rather simple job. (Moaybe not a DIY though).

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

I don't mean to defend my actions about a fix that too is so simple you can not goof up.
Having spent a small portion of my years with The Hydramatic and Allison Transmission Divisions of General Motors Engineering Staff, I always look for an alternate fix that can be performed in the field at the least cost and down time of the vehicle.
I know when a simple fix far exceeds the chance of adding further repairs is not a viable alternate.
The meer chance of the pin retainer falling off and having to remove the valve body un neccesarily is no option in my opinion.
The labor and material cost saving is apparent.
My unconvenional repair is doing quite well, there are no further leaks.
I am not encouraging any one to do as I, just relating that should there be a need there is a method.
Happy Trails Beep Beep from Houston!!!
Donald, El Cheapo

The problem with your repair is as follows.

The round surface that the allen screws into has a relief cut into it so the fluid CAN escape when the orings leak. IT is SUPPOSED to leak when the seals fail.

If you stop up the leak as you did, you are putting hydraulic pressure on the housing which may cause failure, no know, liquids are not compressable.

The B-1 reaction valve is the barrel behind the bolt that is leaking. I have replaced about 1,000 of them. They can be purchased for about $100. or so and install in about 15 minutes. Problem solved. Your dealer is full of crap.

I have only seen one done wrong by another tech and I corrected it. If you buy the NEW valve and o-rings, it will go in smoothly.

__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

Tell me more, you have just hung the carrot in front of the donkey.
Tell me more, part numbers and technique so I can have data when I return to my dealer.
Not having the manual on the automatic I was at the mercy of the technican who did the work.
The placing of the lead gasket was my doing, the RTV was what the technican said he used to correct these leaks.
Unhappy Trails Boo Hoo from Houston!!!
Donald, El Cheapo back fired