It was very first released in 1939 for automobiles. It consists of the fluid coupling and three planetary gears. They collectively make 3 forward and a single reverse speed. There isn't a clutch for engagement and disengagement with the motor. Spur and helical gears are used in the sliding https://damienzmwgo.thekatyblog.com/32560342/a-simple-key-for-gearbox-unveiled