1990 Jeep Cherokee fluid leak

Hi im 17(first car) and been having problems with my transmission is leaking super bad. And I have replaced the front main shaft seal twice none of which was successful, the first time I had replaced the seal I went down to the local parts store and ordered a genaric no name part for $7.00, the second time I had gone to the dealer and bought one for $30.00 and it was a metal one(other was plastic). That still did not work, as you most likely know there are no other parts besides the tourqe converter(but can that leak?) Do think that the bell housing or whatever that connects to it could be cracked, but if was cracked wouldnt I have seen it sence it leaks imideatly that would have to be a big crack-if it was small it would take awhile for it to heat up and expand? So thats what I know it would be great if you guys could help me out. Thanks mike