Rear axle fluid leaks at hub.

[Halbur]

While replacing rear brakes and rotors my buddy and I noticed a little fluid that doesn't belong. We assume it's an axle seal thats just starting to get funky. We plan to replace real soon but could use some help with a couple things. What size is the big nut holding things together inside and will it require a special socket. My research thus far says it's a 2 9/16ths but I can't find anything that says it's anything more than a big nut. Also, I think we need to torque it to 22 ft/lbs and then back it off 30 degrees. Thoughts? The truck is an 06, 2500, mega cab, 4WD. Thanks.