① If the gearbox oil level is too low or too high, check the oil level of the hydraulic transmission oil and adjust the oil level to the specified oil level. The inspection method is: the loader runs for about 5 minutes, and the oil can be discharged from the oil drain switch on the gearbox. If too much oil is discharged and the oil is filled too much, the oil should be partly discharged; if no oil is discharged, the oil level is too low and hydraulic transmission oil should be added.