A gear-shifting device (1) for means of transport including a pair of shafts (20-30) each including a plurality of transmission units (200) wherein each transmission unit (200) of a shaft (30) is rotated by a respective transmission unit (200) of the other shaft (20) wherein the shaft (30) is an activation shaft. The activation shaft (30) includes activation means (40) configured in such a way as to selectively rotate in an integral fashion a transmission unit (200) of the shaft (20) with a transmission unit (200) of the activation shaft (30) by generating a transient difference in speed of rotation between the slowing disk (45) operatively connected to the transmission unit (200) of the shaft (30) and the transmission unit (200) of the shaft (30). The transmission units (200) of the activation shaft (30) rotate freely relative to the activation shaft (30) in a selected configuration of the transmission unit (200).