Gravity displacement method is to remove the oil drain screw of the gearbox after lifting the vehicle, so that the gearbox oil can flow out naturally by gravity.
The replacement method of the circulating machine is to connect the circulating machine, the old oil in the gearbox is pumped out by the circulating machine, and new oil is added to the gearbox at the same time. The advantage of this replacement is that the gearbox can be cleaned.