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