[KrazyCarl92]

Others have already responded with explanations of how the ball shifting mechanism works, but for the sake of the OP I'll answer the question at a higher level.

The idea for both of these shifting mechanisms is to be able to couple and decouple the rotation of gears and their shaft. In both of the styles of shifting gearboxes sold by VexPro you have a first stage reduction of CIM pinions to a larger gear followed by 2 pairs of gears, 1 pair each for high and low gear.

At all times, the high gear gears and low gear gears are meshed. However, the gears that interact with the shifter mechanism (either the ball shifter or dog shifter) have bearings pressed into them to allow them to ride on the shaft but not necessarily have the same rate of rotation as the shaft. When the balls or dog are engaged, the torque applied to the gear will be transferred to the shaft and that particular gear and the shaft will rotate at the same rate. When the balls or dog are disengaged, the gear's rate of rotation is allowed to differ from that of the shaft and torque is not transmitted by that gear to the shaft.

In high gear, the smaller output gear is engaged with the shifting mechanism, its torque is transmitted through the shifting mechanism to the shaft, and the shaft rotates at the same rate as this smaller gear. The larger gear is disengaged and rotates at a slower rate than the shaft without transmitting torque to the shaft, as allowed by the bearing that is pressed into the gear.

In low gear, the larger output gear is engaged with the shifting mechanism, its torque is transmitted through the shifting mechanism to the shaft, and the shaft rotates at the same rate as this larger gear. The smaller gear is disengaged and rotates at a faster rate than the shaft without transmitting torque to the shaft, as allowed by the bearing that is pressed into the gear.

The shifting mechanism and its associated gears and shaft allow for the ability to switch between these two states.