My pinion seal leaked. Had to get it from the dealer, couldn't get one aftermarket. When you remove the pinion flange nut mark the shaft and the nut Rotate the pinion by hand or with a small dial or bar torque wrench to get an idea of the torque required to turn it. Change the seal, and when you reinstall the pinion flange tighten the nut until the mark on the nut is just past the mark on the shaft. Turn the pinion again and make sure that the rotational torque is about the same as when you started. As long as it's about the same you should be good.