It absolutely was 1st introduced in 1939 for vehicles. It is made up of the fluid coupling and 3 planetary gears. They collectively make three ahead and one particular reverse speed. There isn't a clutch for engagement and disengagement from your motor. Bevel gearboxes have spiral and straight tooth https://holdenzzyvs.theblogfairy.com/32974351/indicators-on-gearbox-you-should-know