A 2010 Chevrolet Cruz 1.6AT car with a mileage of about 66 thousand km. The vehicle has no reaction to the hanging gear, and the forward gear is mounted and the accelerator pedal is stepped on. GDS detect fault code P0776 pressure solenoid valve 2 hysteresis closure. Fault diagnosis: hang up and block off, analyze the reverse circuit diagram, and check the components involved in the reverse gear. Through analysis of its oil way: oil pump manual valve clutch selection valve -2 ball valve -3-5-R clutch control valve -3-5-R stop clutch. Through GDS observation, we can see that there should be no problem with its control elements, and there should be an internal pressure relief problem. Steady state adaption found that the 3-5-R stop clutch slips and has pressure relief problem. Through data analysis, it is found that there is no problem in transmission control, but through data comparison, it is found that the internal clutch of the transmission has pressure relief phenomenon. Through the above data analysis, decided to dismantle the transmission inside. After checking the transmission, it is found that the internal 3-5-R clutch clutch spring is broken. Maintenance summary: replacement of internal damage parts, check other related control valve, after loading test everything is normal. Through this maintenance, the author thinks that the most important thing of the automatic transmission is to do well before the dismantling, and make a comparative record of the data and data flow that can be seen so as to achieve rapid and efficient maintenance.