Make sure you check the driveshaft u-joints. The rear u-joint and possibly the yoke, may have some problems. That pinion gear rubbing the carrier shows that the pinion gear had moved back to the carrier and therefore that yoke could be damaged as well. Just a good inspection will reveal problems. The area where the seal rides on the yoke may have grooves and therefore the yoke should be replaced and put a new seal there too and check the axle seals as well on the used axle.