There is no seal at the outer end of the axle tubes. The machined-flat, back side of the axle shaft's yoke fit very close to the tube opening. This keeps out the stones, but water and mud can get in there. The insides of the axle tubes are always dirty which makes it a pain every time you need to remove and install the shafts (its easy to get the splines dirty while installing them and then of course the dirt ends up inside the diff). It would be nice if there were some sort of aftermarket axle tube seal for these trucks, but I've only seen them for Dana 30 and 44 Jeep axles, and that style wouldn't work on our axles because we don't have the room between the yoke and tube end.