Gearbox oil filters are actually hydraulic filters that are used to clean the oil in the flow to lubricate the gearbox. Cylindrical gearbox oil filter and Spin-on screw type is often used for quick replacement. In order to prevent leakage and oil loss, the gearbox oil filter is connected with a rubber o-ring, which is placed in the box of the gearbox filter kit according to the size and pressure of the oil.