My car has been leaking gear oil out of the front differential, so upon inspection my mechanic thinks he sees a hairline crack on the top of it with a mirror & flashlight while it is still on the car. We are taking the differential off tomorrow to see where exactly the leak is & determine what needs to be fixed. I have never heard of a cracked front diff before, has anyone else? it's an 02' turbo with 45k miles. if it is a crack, can the differential be welded?