What is the reason why an automatic transmission car sometimes does not move when shifted into gear?

[Billy]

Here is a detailed introduction to the specific reasons why an automatic transmission car does not move when shifted into gear: 1. Functional obstacle: Generally, the inspection starts from the driving wheels through the rear axle to the drive shaft, then to the transmission, and finally to the clutch. If the drive shaft rotates but the car does not move forward, the fault lies in the rear axle. Lift the rear axle and rotate one rear wheel. If the other rear wheel rotates in the opposite direction but the drive shaft does not rotate, it indicates that all the rivets of the driven bevel gear are broken; if the other rear wheel does not rotate either, the half shaft should be disassembled and inspected for breakage. 2. Transmission fault: If the car is shifted into a certain gear to start but the drive shaft does not rotate, it indicates a fault in the transmission. Remove the transmission cover and inspect whether the transmission shift fork is broken and whether the guide block fixing screws are loose. If the above inspections are normal, perform a gear-shifting test. If the second shaft does not rotate when a certain gear is engaged, it means the half-round key of that gear is broken.