I think the torque spec is 177 ft lbs...i torqued mine to about that maybe 180 or so. I would use blue loctite because you cant get red off unless you heat to like 400 degrees....I think blue works great......if your axles click you know it is getting loose mine was a previous owned car so it had already passed the clicking point....you are suppose to grease the axles too....heres a link that will answer anyones questions on the clicking....but the vibration noise is past the just barely loose point to where it actually wiggles in the hub. Also to answer your question...its the outer nut at the center of the hub.....
Clicking Noise from Rear Axle, - Page 3 - MY350Z.COM Forums