[dmjlambert]

Mine had lots of mud and crud accumulated on the differential. I spent an hour or so scraping and wire brushing and spraying. Here is where the filler plug is on mine, visible from the front passenger side of the differential. There is no drain plug. I removed the cover bolts except just loosened the top one, pried the cover loose, and let the oil drain. The oil has a special stink to it, unlike motor oil. Then cleaned up the cover and gave it a shot of spray paint. I stuck the bolts through a piece of cardboard and cleaned them up and gave the bolt heads a shot of paint too. I let the paint dry a day or two. Fresh gasket and gasket sealer from O'Reilly Auto Parts. I read online some advice about cleaning up the mating surfaces where the gasket goes, put a thin layer of sealant on both sides of the gasket, and fasten the bolts, then letting it sit until dry before adding the oil. So I just added the oil the next day. The differential oil is available in a bottle with a squirt top. I filled it until it drained back out the filler hole, and that was enough. Put the plug back in. I'm probably the only one who took 3 or 4 days to do that oil change. I remember seeing remarks from other forum members that they've never changed the differential oil. My old oil looked pretty good for decades-old oil, and I'll bet it was from 1969.