This animation shows the clutch components and the order of assembly. The final step in the animation depicts the Countershaft gear and hub assembly. The hub, and bearing race are pressed together to trap the gear. The I.D., (inside diameter), of the gear is actually the outer race for the bearings shown...The gear is hardened. If this press fit is not done correctly the inner race, (with ball bearings), will walk off of the hub...The bearings will fall out and the gear will no longer be supported about the hub concentrically.