This is a very special gearbox and motor upgrade. This gearbox uses a powerful 370 motor (instead of the 130 sized original motor) along with a reduction gearbox which is then fed into a transfer case. The metal gears used in the gearbox are 20T metal gears and input shaft into the transfer case is 4mm.
This gearbox if measured correctly has the ability to be upgraded by the user to whatever motor they wish to use as long as the input shaft of 4mm and length of about 13mm from motor is followed. With a different motor option you can either decrease or increase your speed according to the motor KV.