98+ Ranger 4x4's have a D35 front differential that is positioned with its cover plate right up next to a crossmember. That makes it impossible to pull the cover to change the diff fluid in the usual way. The procedure in the factory manual is to use a pump to remove the fluid through the fill hole.
I drilled and tapped the diff case for this low profile motorcycle drain plug to make it easier to do fluid changes. It is tucked up next to and behind two heavy stiffening ribs in the diff case which should make it safe enough for the offroading I usually do. I might someday make set of diff skid plates and include an access hole to the plug.
This type of drain plug is not for every truck. The aluminum case is thin (~3/16") and it would be easy enough to strip the threads if you treated it like the fill plug. I know its limitations and nobody works on my truck but me so I think it will live.