The gearbox is a gearbox that changes the transmission ratio and the direction of motion. between the clutch and the center drive. The main functions are: changing the driving force and driving speed of the vehicle (shifting) when the engine speed and torque remain unchanged; enabling the vehicle to run backwards (reversing); the engine can be stopped without turning off (neutral). According to the transmission type, the gear-type gearbox can be divided into three types: two-shaft type, three-shaft type and composite type. The dual shaft type has two main shafts (excluding the reverse shaft) that are reduced by only one pair of gears. The three-shaft type has three main shafts (first shaft, intermediate shaft, second shaft), which are decelerated by two pairs of gears. Composition consists of two gearboxes in series or in parallel for more gears with fewer gears