The Tamiya 4-speed crank-axle gearbox has four possible gear ratios, including the highest gear ratio of Tamiya's gearbox series, 5402:1, as well as 126:1, 441:1, and 1543:1. This gearbox also features a worm gear, which locks the output shaft when the motor is not turning. A clutch gear prevents the gearbox from destroying itself in case the output shaft gets stuck. The kit comes with all parts necessary to build the gearbox in any of the four possible configurations.

Specs
Typical Operating Voltage: 3V
Gear Ratio Options: 126:1, 441:1, 1543:1, 5402:1
No Load Speed at 3V: 12300 rmp
No Load Current at 3V: 150 mA
Stall Current at 3V: 2100 mA
Stall Torque at 3V: 0.5 oz-in.