The differential was designed to ensure that a vehicle is able to turn a corner as the inside wheel and the outside wheel never cover the same distance when performing a turn. So, the wheels, mounted on the same axle, need to rotate at a different rate. Without a differential, going into and going out of turns would be impossible. So, this mechanism allows drivers to turn a vehicle without the wheels starting to skid. It prevents tyre wear and stops a wheel from dragging. , Having assembled the differential, you can unblock it by pushing the lever in position 1 (up). You can set both wheels in motion by rotating the drive gear. The control lever regulates the smooth locking of the left and right wheels independently by turning left or right respectively. In the "down" position of the lever, both wheels are linked in a rigid coupling and can either rotate together (propelled by the drive gear or a wheel) or are locked in place simultaneously (by the lever of the wheel). Parts count: 92, Assembly time: 1-2 hrs