the differential has 2. one at the top to fill, open this first in case bottom one strips. I would recommend you buy 2 crush washers for the 2 bolts and even the 2 bolts as they are only a few dollars each. The magnet on the drain bolt will have to be cleaned of what it has picked up since the last change. Auto parts stores sell a nifty little pump that screws on the bottle of gear oil so you can refill after draining. Mine works fine, but some have said it is junk.