The gearbox is Level 1 helical gear deceleration device with parallel shaft, using a drum tooth coupling connection of traction motor. Lubrication method of the gearbox is splash oil and mist lubrication, and the gearbox has a good lubrication system. The big gear extracts lubricating oil and casts it towards oil gathering groove of input end and pinion bearing. Lubricating oil does not leak under various operating condition. Oil filling plug and oil drainage plug both apply magnetic plug. Texture of the gearbox adopts the housing of cast-iron split-type structure. One end of the gear reducer box body is installed on the shaft through the bearing, and the other end of the gearbox housing is tilt hang on the frame beam through the boom with anti-vibration rubber. The gear is made of high-quality nickel chrome molybdenum steel, and gear grinding is done after carburizing and quenching heat treatment. Micro precision grinding and modification is done on gear tooth part, to ensure good operation under various operating conditions.