The axle itself would not leak. However there is a seal that it passes threw to connect to the transmission that can.
Axle can go bad, hard driving and jack-rabbit take offs will make it's toll on them (not saying you do that) an axle can run about 60 for a reman maybe alittle more. To have a shop do it add on another 75-85 depending on there hour rate. And request they change the seal which cost about 3 bucks or so. Could be looking at 140-180 depending on the shop and the hour/part markup charge.
