extension housing leak

i have a 95' xj sport. my rear extension housing is leaking tranny fluid everywhere i replaced the housing with my fathers broken down 92' xj which has been sitting for about a year now. it still leaks.... do you think that i need a new extension housing or the mainshaft is slightly bent? the parts i have taken off my fathers jeep in the past have all gone to hell and i have had to gop out and buy new parts and do the job again this could be one of those situations but i dont know.

There is a bushing inside and a seal at the tip. They both do wear out. It is common to wear a grove in the driveshaft yoke. Therfore you would need a new yoke.