Looking into this leak, seems to be leaking through this 12789088 shaft seal.
Doesn't appear to be in bad shape. The intermediate shaft looks to be hollow. I'm not sure if there would normally be any substantial amount of trans fluid in there, maybe I just over filled it?
Can't get a new seal locally. It looks like it rides on and spins with both shafts, so I'm thinking I might just load it up with RTV and see if it holds.