After a week of idleness at the end of the National Day, we restarted our record of repairing gearboxes. I remember that we introduced Buick of American cars and Japanese CVT. Today we will talk about our French cars, which are famous for their romance, and the French system represents our Peugeot cars. It is equipped with an AL4 electronically controlled automatic gearbox, which is jointly developed and designed by the French PSA Group and Renault. This kind of automatic transmission is mainly used in Fukang, Elysee, Picasso, Citroen C5 and other imported Citroen, Peugeot and Renault cars. After the Peugeot 307 suddenly heard the sound of “drip, drip, drip” during normal driving, the triangle warning light on the dashboard turned on, and the driving computer showed that the gearbox malfunctioned. At the same time, there was a sense of frustration while driving, and a noise appeared at the bottom of the car. It seems inevitable to repair the gearbox. How much does it cost to repair the gearbox? After reading all this, you will have a number in mind.

Needless to say, the car is directly on the shelf, because the gearbox is connected to the front wheel axle, so the two front wheels must be removed, the transmission peripheral screws must be removed from below, and the gearbox and the engine must be separated.

The car’s gearbox and engine are positioned laterally, and the two parts, the flywheel and the torque converter, want to be connected to transmit power.

The brother of the whole car team has helped us to lift the gearbox down from under the whole car and put it on the maintenance station. the master pulled out the gearbox torsion without saying a word, and the gearbox oil spilled out immediately. Look at the look of this oil product. Without saying much, it has become brown, and you can imagine how much mud mixture there is inside.


This is a hydraulic torque converter, which is a non-rigid torque converter with liquid as the working medium, which is one of the forms of hydraulic transmission. It has a closed working cavity in which the liquid circulates, in which the pump wheel, the turbine and the guide wheel are respectively connected with the input shaft, the output shaft and the shell. When the power engine (internal combustion engine, motor, etc.) drives the input shaft to rotate, the liquid flows out of the centrifugal pump wheel, passes through the turbine, guide wheel and then returns to the pump wheel, and circulates again and again. The pump wheel transfers the mechanical energy of the input shaft to the liquid. The high-speed liquid rotates the turbine and transfers energy to the output shaft.

After removing the torque converter, let’s take a look. His front oil seal and oil pump rubber ring are behind the torque converter, while the half-shaft oil seal is in the lower left corner of the gearbox. Why do you say this? because, in fact, many riders also report that there is a lot of oil leakage in the AL4 gearbox, so here we can easily show you the oil leakage. We will continue to remove it in view of this failure.

The black part below is the oil pan of our AL4 gearbox, and the valve body of the gearbox and the computer are removed.

The valve body of the automatic transmission is a rectangular aluminum block with multiple valve channels inside, which shifts the clutch group of the mechanical part of the gearbox by adjusting the oil pressure. Therefore, if the gearbox valve body appears wear and tear, it will lead to oil pressure relief inside the valve body, which will lead to oil pressure instability, which will lead to a sudden setback impact on the vehicle. Valve body damage installation valve above the solenoid valve will timely detect the fault signal to form a fault code and finally turn on the fault light on the dashboard.

Therefore, the valve body of the gearbox must be tested and repaired with special equipment. If the detection linear fluctuation is relatively large or there is a deviation from the factory standard value, it can only be replaced if it can not be repaired.

With the turn-off shell, we can clearly see the internal of the automatic transmission, differential, bearing, oil pump, oil grid and so on.

The biggest one on the table is our differential.

This gearbox is easy to ablation here, especially the small bearing is very easy to break, which is also a common fault.

The oil pump of the gearbox is installed behind the torque converter and is driven by the shaft sleeve behind the torque converter to provide hydraulic oil with a certain pressure and flow for the hydraulic control system inside the torque converter and the gearbox to ensure the lubrication of the planetary gear mechanism and other friction pairs. What is the point that we need to pay attention to here?
That is, the piston at the opening of the gearbox oil pump is easy to go wrong. Once there is a problem and the oil pressure of the oil pump cannot keep up, it is very easy to release the pressure, causing the gearbox to slip.

Input shaft clutch cup

Take apart the clutch and take out the friction plate that has been blackened like this. It can’t be used at all. It’s strange not to turn on the fault light.

To this piece of AL4 gearbox is completely disassembled, through the whole disassembly process, the owner of the car has skidded and changed gears frustrated, mainly due to the aging of the piston sealing ring caused by pressure relief can not be fully combined with the friction plate, the emergence of poor combination caused by abnormal wear of the friction plate. After ablation, the friction coefficient between the friction plates decreases, and then skidding occurs. The iron filings ablated by the friction plate are mixed in the oil, which will enter the valve body, and if it is serious, it will lead to wear and tear of the valve channel inside the valve body, resulting in excessive fit clearance, which will lead to a sudden setback in the shift or delay in rising gear, locking and so on. Therefore, if there is a problem with the car, it is necessary to determine the point of failure as soon as possible to avoid further damage.

All right, leave me a message for more gearbox questions. You are welcome to communicate with me more in the comments area below or search for various problems and maintenance plans of Xinfumei gearbox maintenance. Thank you!