If you refill the diff. you might consider NOT fillng it as much as the book says (to the point of coming out the fill hole). 1/2" or so below is the advice I've read, stick your pinkie in the opening and bend that first knuckle joint down, when you get oil on it, stop.
I drained and filled mine this spring, shortly after BOTH hubs were dumping oil on the brakes, coincidence? Maybe, but after rebuilding the hubs; oil seals, bearings, shoes, cylinders and all, I refilled as advised above.