sounds like you've read the part in the Bentley repair manual where it says one of the common faults of the Audi A4 transmission is a leak between the motor and transmsission. Bentley goes on to say that the bronze bushing that's pressed into the pump housing (that the torque converter spins in) commonly wears enough to allow a fluid leak.
I think the bushing wears enough to allow the torque converter to move off center, pressing on the seal enough in one direction to allow the ATF to leak by.
The bushing and seal are available aftermarket, as is the pump housing if you choose to go that route. The torque converter generally needs to be replaced, too, because of wear on the surface that rides on the bushing.