On the bottom of the torque converter housing there is (or in my case, was) a plastic cover shown in
the parts list as

NJA 4465 AA Stoneguard Gearbox Torque Converter Housing Solid.

Is this a cover for an inspection port or what? I'm not sure why there is an opening in the housing.

 

You'll find out if you ever need to take the transmission off. It's the way to access the Torque Converter bolts:





Graham