New Five-Speed Automatic Transmission for FWD Vehicles

AISIN AW has developed a five-speed automatic transmission “55-50SN” for front wheel drive (FWD) vehicles. This new 55-50SN has been developed with a concept to minimize length and mass increase compared with the current four-speed automatic transmission, and is one of the most compact five-speed automatic transmissions in the world. This has been accomplished by newly developed planetary gear sets, a new differential, and a new squeezed torque converter. In addition, the control system is made by a unique design to maintain the excellent compactness and to achieve a high quality smooth shift feeling. This paper describes the construction, characteristic, and function of this five-speed automatic transmission.