Originally posted by illflem
Perry, If the leak happened just after work on the front end, such as brake rotor replacement, it will most likely stop on it's own. Just wait it out. Another possibility is that vent line is clogged, it comes off the passenger side axle housing ending up near the air box. Easy way to check the vent is to drive the truck for awhile then open the fill plug on the differential while listening for air hissing out. Make sure the differential isn't overfilled at the same time, the truck must be level side to side and front to rear. If it is a bad seal it is just the seal that needs replacement, problem is it's location, it goes in from inside the differential housing, the differential guts and axle will need to be removed and special tools will be needed. The passenger side is harder to do than the drivers. While you can fabricate your own tools easily I find that it is one of the few jobs left to the dealer, they charge around $150 and it is well worth it.