Less than a year ago, I replaced all my wheel hubs. The other day, while driving in reverse I noticed a clunking noise. No noise while driving forward. Brought it in the garage and jacked the rear end up. Wiggled the left rear wheel, unbelievable amount of play. Took off the wheel. I noticed the cotter pin was still trough the nut on the shaft. Took off the hub and noticed that the key had just about disintegrated. Couldn't believe it. Of course the tapered hole is worn out. Not sure what happened. I bought the key stock at Tractor Supply. My guess it was too hardened steel. Called PT new hub is $64 plus shipping.