How old is the oil in the differential? When it gets old, it get thin. Many rear axle seal leaks have been remedied by just changing the oil! No guarantee, but if you are up for it try it, the seals may leak a little until the new oil softens the old seals, so I would try it for just a few miles, then if the leak persists, change the axles seals. You needed to change the rear end oil anyway!
