370Z Rear axle clicking - Repair -with upgraded Kawasaki Axle Nut!

As part of my channel I buy and sell cars as a hobby..My 2011 Nissan 370Z roadster has the very common rear axle nut noise ..We upgraded w a Kawasaki axle nut Part # 922100280- 2 Nissan axle washers(3 total) and cotter pin..$60 in parts! But I did 1 side of car so really its $30 per side for parts!