It was first released in 1939 for cars. It is made up of the fluid coupling and 3 planetary gears. They collectively make three ahead and 1 reverse velocity. There isn't any clutch for engagement and disengagement in the motor. Spur and helical gears are used in the sliding https://gearbox42964.blogunteer.com/32800931/a-simple-key-for-gearbox-unveiled