willysmjeeps.com

I'm fixing to rebuild and paint my front axle. Can someone tell me if the ball at the ends of the axle gets painted?

No the knuckle surface is not painted. Even if it were, the movement of the axle back forth and the rubbing of the knuckle seals would remove the paint eventually. You can paint up to the point at which the seals don't travel. Otherwise, give the bare metal a coating of grease until the axle is installed to keep it rust-free. Thereafter, if the jeep is stored immobile for a length of time, another coating of grease will keep rust away. You want to avoid having the surface of the knuckle pitted by rust.

The surface of the ball that is swept by the seal is not normally painted.

Perfect, that's exactly the info I needed.