Is the drain/fill plugs on our transfer cases really a 30mm. It feels a little sloppy.

pretty sure it's a 1 and 3/16

I couldn't get mine off with a crescent wrench so I looked it up and it is a 30mm. I picked up a new 30mm socket and it fit tight and easily got the plug off. Could be your socket is a bit worn out, or maybe the plug is a bit worn from a PO removing it using the wrong tool.