John:

The sealant listed is Omnifit FD 3041 sealant (50 ml), part number 002 989 47 20 10.

This might be terminologies but here is how I understand it.

The "input" is really the mating between the transmission and the transfer case. The T case in installed dry onto the transmission. ATF is then filed until it runs out from the filler plug.

Then there are two "outputs", one to the front and one to the rear. There should be seals for both.

From what I have communicated with other 4Matic members, you leak is most likely NOT from any of these seals but from where the T case mates with the transmission. If you examine really carefully, you should see wetness only below any of theses output shafts or seals.

The bad news is that you have to remove the T case for any work on it.

That would be my guess (might be an uneducated one).