It had been 1st introduced in 1939 for automobiles. It is made up of the fluid coupling and 3 planetary gears. They collectively make 3 ahead and one reverse speed. There's no clutch for engagement and disengagement in the engine. The copyright which unites the many planetary gears revives https://gearbox32074.answerblogs.com/34011167/not-known-details-about-gearbox