If you didn't hear it until now, it obviously has something to do with the new wheels. I'm still thinking it's the rear lugs. I had the same issue and knew right away what is was. I put it back on the lift and also didn't hear anything; however, when turning the rear wheels slowly, I could feel the lugs hitting. After inspecting the lugs, there were no signs of rubbing, but I still knew it was the issue. The springs give enough to not leave marks on the lugs. I ground about a 1/4 inch from each lug and put 'em back on. Good as new.