You probably have found the problem with that half-axle. Certainly the differential seems good.
It probably depends on the exact nature of the problem, but a lot of half-axle problems show up on tight, slow-speed turns. Kind of a whump, whump whump from the side opposite of the direction you turn (its moving faster under more stress).
The condition you describe may not actually cause you a problem for some time, but may well be an indication of some wear.
That's the best I can do for an Internet diagnosis!
Ken300D