The mileage is about 19 thousand km, with 2011 KIA Freddy cars equipped with 1.6L engines. Customer response: the gearbox has abnormal noise after the vehicle is suspended. Fault diagnosis: according to the customer description, the fault of the car is that the abnormal noise similar to the gear meshing can be heard in the cab, but it is normal, without any noise. The noise was not so obvious at first, and the customer didn't care too much, but the noise was getting more and more serious recently, so the customer sent the car to my shop for repair. After receiving the car, the maintenance personnel carried out the road test to the malfunction vehicle, indeed, as described by the customer, the transmission is hung in the forward gear. The 1~5 gear is normal and there is no abnormal noise. But when the transmission is put into the reverse gear, the sound of metal knocking, which is similar to the gear without engagement, will be heard in the driving room, especially in the driving room. It is the most violent when the driver raises the clutch pedal to half. When the clutch pedal is completely lifted, the noise will be smaller, but it still exists, and the noise will disappear when the driver completely steps down the clutch pedal. When the prize vehicle goes to the maintenance station and lift up with the lifting machine, the car hangs down the analog road test. At this time, the maintenance personnel look for the noise source from the bottom of the car. By comparing the noise, it is found that the noise is most obvious in the middle of the transmission, and the noise will disappear after the clutch is stepped on the clutch, so that we will get the noise. It is preliminarily considered that the fault point is inside the transmission. Thus, after communicating with customers and obtaining customer's permission, the maintenance personnel disassembled and decomposed the transmission of the vehicle. Ferretti's manual block is equipped with M5CF1 manual transmission. This transmission and its improved type are used in many models. Usually the internal faults of the manual transmission can be found and determined through a direct observation, but when we decompose the transmission of the malfunction vehicle, there is no unusually worn or loose parts in the transmission. Next, the maintenance personnel are reassembled and installed on the vehicle according to the standards of the maintenance manual. Once again, the test run shows that the fault remains unchanged. At this time the maintenance personnel put forward the idea to replace the transmission assembly for the customers, but in the transmission of the transmission we did not find that the transmission has any problems, if such a blind replacement of the transmission is not appropriate. So we re analyzed the fault of the car again, assuming that the transmission does not have a fault, then the component associated with the fault is only the clutch, although the noise will disappear after stepping on the clutch pedal, but the clutch is in a state of separation, and the detached piece is not forced. When the driver gradually lifted the clutch pedal to make the clutch gradually joins, the clutch began to gradually force, and the noise appeared at this time, so it seemed that the possibility of the clutch disc had a great possibility. If clutch disc is the problem, why is there no noise in the gearbox when moving forward, and when there is noise in the gearbox when reversing gear? This is probably related to the larger torque and the direction of rotation when reversing gear. Through the above analysis, we disassemble the transmission again, then disassemble the clutch disc and clutch from the engine, and directly see no problem of the two parts, and it is impossible for the equipment in our store to perform a separate performance on the parts such as the clutch. Test. In this case, we can only change the clutch disc and the clutch pressure plate first. Replace a new clutch press disc and clutch plate, and then install the transmission again on the car and start the engine test. This time the noise disappears when it is found, we can also make sure that the noise of the car is produced by the clutch. Later, this kind of fault has appeared on the imported KIA 1.6L manual type. It is also the noise when hanging the gear. It is normal to hang forward. It is also the problem to be solved after changing the clutch disc and the clutch plate.