When i first purchased my samurai (1987) i put a locker in the front diff.   When i put it back in after refilling the diff with oil in noticed after driving it for a while a leak (driver side) occurred from the knuckle just above the lower king pin where the axle housing and knuckle meat so i replaced the oil seal and felt pad, and it still leaked and now the passanger side is leaking as well.

In my diagnosis i noticed that there was play, up and down, in the knuckle so i just order a complete rebuild kit for both sides (king pin bearings and wheel bearings etc.....) i will be starting on it soon and will update as i make my progress.