I have a 722.418 transmission. I have finally isolated my leak. Just above the pan, just under the cooling line, on the left side of the transmission just behind the bell housing, there is some sort of a plug about the size of a half dollar that takes a 14mm Allen wrench. This is the source of the leak...it appears to be fully tightened.

What is this? Can it be easily resealed? What do I need to do? Is there any risk?

Thanks for any help/advice anyone can provide.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife