A Lexus ES240 car. The automatic transmission of the car is abnormal high temperature and 5 gear skidding. Inspection and analysis: after understanding, the car first appeared abnormal noise at high speed, then completely unable to drive. So it was dragged into the repair shop for repair. At that time, it was found that the oil bottom shell of the automatic transmission was deformed and the filter was blocked, resulting in the poor oil supply of the automatic transmission oil (ATF), which caused the damage of the CO and the C3 clutch. After the automatic transmission has been repaired, there is a phenomenon that the temperature of the transmission oil is too high (over 130 degrees centigrade) and the 5 gear is slippery. Check automatic transmission oil level, normal; measurement of automatic transmission related oil pressure, also in the normal range; stall test, stall speed is also in the normal range. Read the fault code of the automatic transmission system, store no fault code, read the data stream, and find no obvious exception. To avoid the possibility of the high temperature of the automatic transmission caused by the radiator problem, the above failures still exist before replacing the radiator. In addition to the disintegration of the automatic transmission, it is found that there is no other exception except that the C3 clutch is slightly worn and blackened. The piston and sealing ring of the C3 clutch are normal; the C3 clutch is replaced, and the automatic transmission is installed after adjusting the gap, and then the test car is carried out again, and it is found that the automatic transmission has normal jump gear. But the temperature of ATF increases rapidly as the speed increases. When the temperature of ATF rises to 130 degrees C, the car does not continue to speed up. At this time, the temperature of the ATF is gradually reduced as the speed decreases. Through trial run, it was also found that as long as the automatic transmission reaches 5 gears, the temperature of ATF will increase with the increase of vehicle speed. According to the maintenance experience, the reason that the ATF temperature is too high in the high speed gear is usually the failure of the locking clutch inside the torque converter, or the insufficient oil supply pressure of the torque converter lock clutch causes the lock clutch to slip. Re check the valve body and find that the locking control valve is worn out and there is a hairpin phenomenon. The failure of another body assembly is tested on a failed vehicle. Troubleshooting: replace the automatic transmission valve assembly.