Mainly, the automatic gearbox uses a roller clutch for plan upshifts/downshifts. It operates much like a ratchet. It transmits the torque only in one way by cost-free-wheeling or overrunning in the other. The benefit of this kind of clutch is that it eradicates the opportunity of concurrently applying the clutch https://gearboxauto04702.ampedpages.com/everything-about-gearbox-auto-60774960