"Fit each [synchro ring] to the tapered cone on its corresponding gear. There should be a clear gap between the inside edge of the ring and the gear, around .063 inches/1.6mm where a new ring is used on a new or little-worn gear. Less than 0.031 inches/0.8mm means the ring needs replacing. If this dimension isn't greater than one with a new ring (the gear cone surface is worn) a new gear is needed. Fits the smooth and rib case.