Pinion seal, I don't know the cheapest place to get it. Are you certain it is not just overfilled? That will make them leak, or, is it a gusher or an occasional drop? For the occasional drop I wouldn't do a thing except check the level often and park on something I didn't care about getting some oil on. Changing the pinion seal is no big deal, getting the right torque back on the pinion shaft is something that many at the Dumb *** Dealerships say they can do but really don't know how to do without damaging the pinion bearings when they go back with it. That "I can tell by the sound of the impact wrench" style is what I am talking, writing, about. 106