You shouldn't need a socket. There is a cotter pin going through the nut, remove that then the nut should be loose enough to remove by hand. Do not over tighten it when you put it back together and don't forget the cotter pin.
If its 4x4 is a big one. I dont remember what size it is but its one that comes in the standard sets you can buy. Sometimes you need the ones made for axle nuts with the thinner side wall to fit in the recess. Standard sockets that big tend to have fairly thick sidewalls and sometimes dont fit.
