Common Faults of Transmission

Common faults of transmission

1. Oil leakage

There is oil leakage at the gearbox housing or oil pan. One reason is that the seal is aging and poor sealing; Another reason is that the shell has trachoma due to poor manufacturing process.

2. When D or R is engaged and the engine is shut down, this fault may be caused by damage to the locking solenoid valve or card jamming of the locking control valve.

Engage D or R gear, and then release the brake, the vehicle does not move. Or the car can travel a short distance after the cold start, but the car can't travel under the hot state. This situation is mostly caused by damage to the input shaft or reverse clutch, or damage to the D / R brake. It may also be that the automatic transmission has serious oil leakage and serious oil shortage; The connecting rod or cable between the shift lever and the rocker arm of the manual valve is loose, and the manual valve remains in the neutral or parking position;

3. The gearbox slips and the acceleration is weak; Transmission water inlet

When the car is driving, there is a sound of engine idling during the acceleration of the fuel door. The car speed has not increased. I feel that the whole car is weak. Most of this phenomenon is caused by the burning of the clutch plate. The gearbox works abnormally due to water inflow from external reasons. This may be due to oil spilling in the water tank or water entering from the ventilation cap of the gearbox.

4. Peculiar smell in the box

The gearbox works by hydraulic oil. When the oil temperature is too high, some combustion will occur, and these peculiar smell will be transmitted, which indicates that some executive parts in the gearbox do not work normally.

5. High engine speed during driving

This problem includes two situations: high speed during smooth driving and high speed during acceleration: high speed during smooth driving and easy to test, such as an engine displacement of 2. The vehicle speed of 0 can reach 100 km at 2600 revolutions at ordinary times. If it often takes 3000 revolutions or more to reach 100 km for a period of time, it indicates this fault. Generally, this fault is caused by the failure of the high-speed gear of the transmission or the failure of the lock up clutch inside the knob, and the transmission needs to be repaired immediately. The speed is too high during the acceleration process. This fault test is a little complicated, because during the acceleration process, the increase of engine speed is closely related to the accelerator pedal. For example, a normal Passat can accelerate the vehicle when the engine body speed is 2500 RPM under the condition of small throttle, but the engine will increase to 5500-6000 RPM under the condition of full throttle, Such a huge contrast is due to the fuzzy logic control of the electronic control system of the gearbox, so this standard needs a certain professional level to complete.

6. Engine stalling, no reaction and impact in gear

The test gear entry standard is to start the engine, idle, step on the brake and enter the gear. The normal situation is that you feel like entering the gear within 1-1.2 seconds and release the brake pedal. Without stepping on the accelerator pedal, the vehicle will start slowly and gradually extract the speed of 10-20 km / h. this is a normal gear entry standard. If you enter the gear for more than 2 seconds, you will locate the gear entry delay, This situation requires immediate maintenance; If there is a strong impact feeling in gear, that is, the impact of positioning into gear, it should be noted that any automatic transmission has a certain degree of impact feeling in gear. If there is no feeling at all, it indicates that there is an internal fault, but the impact is relatively large, which is unacceptable. The problem caused is very complex, including many aspects except the gearbox; The situation of stalling is that the engine will stall when shifting in. This problem is more obvious when the car is cold. This problem is caused by the gearbox and other body systems.

7. The oil inlet filter screen is blocked; Serious leakage of main oil circuit; The oil pump is damaged.

Shifting impact and impulse of the vehicle during driving are also common faults of the automatic transmission, which may be caused by the sticking of the valve body due to dirty transmission oil.

8. Abnormal sound

1) . it is the abnormal sound of the bearing. Generally, the abnormal sound of the bearing is closely related to the speed. The higher the speed, the more screams.

2) . the differential or main drive gear makes abnormal noise. This abnormal noise is generally obvious at the speed of 50-70km. Because the meshing surfaces of the gears are different, the noise is generally obvious when refueling, and the sound when loosening the accelerator is obviously weakened.

3) It is the abnormal sound of the hydraulic system such as the oil pump. This sound is closely related to the speed, but has nothing to do with the speed. When the speed is high, the oil suction of the oil pump is blocked, resulting in scream. It should be noted that the transmission system works together with the engine, chassis and other parts. Many sounds are mixed together, which is not easy to identify.

9. The automatic shift time is too long or too short

Generally, the automatic transmission has a specific shift speed and speed. If the shift time is suddenly too long or too short, it means that the transmission ratio of the transmission is out of proportion. At the same time, it will feel that the engine speed is too high. What's more, the transmission does not shift, which indicates that there is a problem with the transmission.

10. Engine idling

Engine idling generally occurs in two situations. One is that the engine idling suddenly occurs when the vehicle is stable and returns to normal when the speed slows down. This situation generally indicates that the gearbox suddenly drops from high gear to low gear in a short time. The problem may be in the control system or heat dissipation system, and there is no problem with the gearbox itself. The second is that there is a short slip and idling phenomenon in the process of acceleration or shift. The intuitive feeling is that the latter is not as powerful as the former. In fact, it is exactly the opposite. Most of the problems of the latter lie in the clutch and other related links in the gearbox. It is necessary to completely disassemble and overhaul the gearbox, and the time and cost consumption are much more than the former.

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