Originally Posted by Unclemeaty

I second; everyone should check your rear axle nut on the driver's side. 2009 370z did not use a locking sleeve over the axle nut like 2010 and 2011 model Zs, and this can cause the axle nut to loosen up about 2-4 turns before being stopped by the cotter pin. Threadlock, a 1.25" deep socket, and a proper torque wrench should do the trick.