If you want to make a special socket for it, get one that will fit around the outside of the nut, drill 2 holes opposite of each other on the top portion of the socket and put a hardened pin through it, the idea is for it to act like a wide slotted screwdriver. File the ends flush with the socket walls, use your 3/8 socket wrench and now you have a tool that will give you more power to unscrew that pesky nut.