My understanding is that the knuckles call for gear oil and this is what lubricates the inner and outer wheel bearings and knuckle bearings as well as the u-joint in the axle shaft. When I took mine apart, those wheel bearings were pretty dry. Knuckle bearings were shot. My solution was to pack all the bearings with grease like conventional bearings found in an open knuckle system or two wheel drive. So far so good. I figure if I stick to a 10,000 mile service interval, I will re-pack about every seven years. And no oil spots.
