I just rotated my tires and noticed the noise others are describing in this thread and couldn't figure it out. Google led me here! I'm tired of waiting on service centers or mobile techs, so if it's something as simple as a loose axle nut I was going to take it on myself before I called for help.
I picked up a 32mm socket from Harbor Freight ($5) and removed the axle nut with a breaker bar. It wasn't very difficult to get off, but it was tightened. There was no existing grease so I didn't add any, I just wiped it out with a towel. Since I don't have a torque wrench that goes up to 180lb/ft, I torqued it with my breaker bar as tight as I could (just like the mobile service guy from earlier in the thread did). The noise was gone. Easy fix!