I put a dial indicator on the back of the ring gear and had .005 run out high to low. Then I checked the back lash and found it ran from .007 to .012. As I said when I spoke to the vendor he didn't think I would have a problem. I will call him again and ask if he has another set to exchange with. It took him almost 2 months to get the last set to me. I think he gets them from China. He seemed like a straight guy so I hope I don't have a problem.