What does 9AT mean?

[MichaelLee]

9AT refers to a 9-speed automatic transmission, where AT stands for torque converter automatic transmission, and the number 9 indicates nine forward gears. The 9AT transmission uses shift elements to control different combinations of planetary gears, achieving a configuration of nine forward gears and one reverse gear. It employs nested planetary gears to reduce the transmission's length and optimizes the transmission structure while using lightweight component materials that meet strength requirements to control overall weight. The advantages of the 9AT transmission include fuel efficiency and rapid acceleration. Its core structure consists of four sets of planetary gears and six shift elements, one more than the 8HP transmission. With multiple gears, the gear ratio difference between each gear is reduced, providing a wide range of reduction ratios. This allows for strong acceleration at high speeds while maintaining low engine RPM.