03-04 o/d housings crack at the bottom on the passenger side bolt at the bottom. You can take the overdrive housing off but if there is metal contamination i would go through the whole thing.
If your housing is leaking go to the dealer to order a new one and be done with it.Good luck finding a good used one.
I would check cooler flow and remove the check ball in the cooler line if it has not been done already.
I have rebuilt many of these transmissions and very seldom is there a problem after the overhaul.
There are many things to help cooler flow during the rebuild process which your builder should of fixed for you.