When the strain drops, springs lead to the clutch to release. Evenly spaced ridges, termed splines, line the inside and outside with the clutch to lock into the gears as well as the clutch housing. You could read more details on these clutches in How Automatic Transmissions Do the job. https://clutch-plate32063.theblogfairy.com/32247400/getting-my-clutch-plate-to-work