It would sure help if you told us a little more about the hole. Did you break the diff and poke a hole from the inside? Did you drive over something and poke a hole from the outside? How big is the hole?
Aluminum housings often can be welded, depending on the nature of the damage and the location. If there is no damage inside and there is access, talk to a welding shop that is familiar with welding aluminum and see what they can do. If you blew the diff and ventalated the case, it is probably time to look for a wrecking yard trans.
