First of all, make sure that the machine is at a standstill and in a cold state, and that the temperature of the gear oil does not exceed 50 degrees. Secondly, unscrew the oil drain plug at the bottom of the gearbox, and use a bucket to catch the waste oil until the oil drain port leaks out in the form of a drop. Then flush the gearbox with new oil. After that, unscrew the oil drain plug and refill the new oil to the specified level. Gear oil to petroleum lubricant base oil or synthetic lubricant-based, adding extreme pressure anti-wear agents and oily agent modulation and become an important lubricant.