AT are installed before torque from the engine is transferred to the tires. They consist of the following three elements and serve to transfer torque from the engine to the tires while automatically shifting gears in response to the vehicle's driving conditions.

♦The three elements of the AT

1. Torque converter

The torque converter transfers torque from the engine to the planetary gear train.

2. Planetary gear train

The planetary gear train consists of planetary gears, a clutch, and a brake. By switching between combinations of planetary gears, the transmission can select the gear that best suits the vehicle's driving conditions.

3. Hydraulic control system (valve body)

The hydraulic control system senses the vehicle's driving conditions, converts signals output by an onboard computer into oil pressure, and issues instructions to the planetary gear train to shift gears (gear shift or reverse rotation).

♦AT mechanism