[W126 Coupe] Transmission is creating a river

[David Fatovic]

Does the torque converter have a seal inside of the
bell housing?  On my dad's 85 500SEL he was
complaining of losing too much transmission fluid.  I
did some work on it today first cleaning all around. 
I didn't see any obvious leaks, and everyting looked
tight.  I put some more fluid in and ran the car for a
while while it was still up on jack stands.  I did not
see any leak, nothing was coming out.  So I decided to
take it for a little test drive.  I drove it around
the block and when I got back, the transmission fluid
was pouring out of the slots at the bottom of the bell
housing.  So it didn't leak until I put it in gear.  

Any ideas of what could be leaking inside?

Thanks,

David