What size socket to remove fill plug from differential ?

Most are just a 1/2" square plug, you just a use a 1/2" drive long ratchet with no socket. Some are opposite (the square sticks out). I think it's a 3/4" in that case, but I'm not sure, I have an 8 point socket for them. There there's also dome hex ones out there, no clue on what size they are, I use the wrench that fits It's been a while since I ran across a hex plug.

 

My diff plugs are not recessed 1/2" plugs like on my transmission. They are square outset plugs. I just use a large crescent wrench and remove them to check the level.

 

I changed mine from the original 1/2" ratchet type cause I would tighten too much putting them in & almost had a problem 1 time trying to get out. so I put in the magnetic type out set & also just use a big crescent. same with oil pan drain plug.

 

Most rear end if square is out is 5/8 most trans are 15/16 or the 1/2 internal but on rear end they sometimes use 11/16 or 3/4