Cool. Thanks for all the suggestions everyone. My son and I were having a measurement system accuracy discussion when doing our backlash checks. Having a good repeatable set up seems important. The one piece that I don't ever see addressed is if the movement of the dial indicator shaft should be parallel with the "rotation" of the ring gear (parallel with the ring gear bolt face) or perpendicular to the gear. Does that make sense? FBird - I know this is exactly what you are getting at above and I just want to make sure I understand what you were saying.