Well my drivers side hub is leaking real bad. the passenger side is fine. they resealed the hub with new gaskets and still is leaking. they said the knuckle area of the axle may need work. on the inside of the wheel there is grease on the ball.?
you need the knuckle rebuild kit and make sure it includes inner axle seals. Those inner seals separate the 90-wt in the diff from the moly lube in the knuckle. The knuckle felts/seals (where you see the grease) is a common leak point...mine are always greasy looking.
IMO, if it don't drip on yer floor, it ain't a problem yet.
See Morgan's writeup in the Tech Links for the process.