1999 Jeep Cherokee transfer case rear seal

Had an auto shop doing some work on replacing noisy bearings recently, one of which invovled taking off the transfer case and replacing the rear seal going to the drive shaft. Before they got hold of it, this car never leaked a drop of anything, now, leaks like a sieve. Took the liberty of looking at someone else's jeep in the parking lot, they have put 2 pipe clamps around the seal to keep it from leaking. Is this normal? Or is there something else I should be looking for that maybe the shop doesn't know to look for? Drive shaft slings fluid all over exhaust, car smokes every time I drive it.