The mileage is over 270 thousand km, and the 2005 TOYOTA crown car is GRS182L. User response: the vehicle will vibrate at a constant speed of 80 km/h. If the vehicle continues to run at this speed, the vibration will intensify. As long as the speed of this car is avoided, everything is normal. Inspection and analysis: the maintenance personnel first check the transmission parts and tyres of the vehicle, and find no abnormal beating. After balancing the tire, the failure is still. Check engine and transmission control unit, trouble free code. Test run at idle speed, engine speed up smoothly, no abnormal jitter. The engine stall test, the D speed 2300 r/min and the R stall speed 2150 r/min, indicate that the torque output of the engine and the torque converter are all normal. Measure the oil pressure of the transmission. Do not step on the accelerator pedal, D block 390 kPa (normal range 361~421 kPa), R block 490 kPa (normal range 482~562 kPa); acceleration pedal to the end of the D block 1280 kPa (normal range 1245~1 345kPa), R block 1575 kPa (normal range 1472~1612 kPa). The oil pressure is in the normal range. Observing the data flow recorded in the road test, it is found that in the speed point of body vibration, the transmission is in the 6 gear, the opening of the throttle is constant, and the torque converter locking clutch is locked. From the data flow of the speed sensor SP2 of the transmission output shaft, it can be seen that the output shaft speed also fluctuates, which is consistent with the body jitter frequency. According to the analysis of data flow, the actual observation of the locking clutch is decided. When the vehicle vibrates, the lock solenoid valve is closed with the active test function of the fault detector. Release the lock clutch. After the instruction is executed, the movement immediately disappears; the vibration of the solenoid valve appears immediately. The result of this test shows that the problem of the vehicle is the resonance between the transmission part and the engine crankshaft. Under normal conditions, the damping of the lock clutch damper can eliminate this resonance, but in the case of spring aging, the resonant frequency of the damper may be offset. After checking the torque converter, it is found that the spring of the shock absorber obviously shows signs of aging, indicating that the test is correct. Troubleshooting: replace torque converter, test run to confirm troubleshooting.