One-Way Clutch, A/T

PRIMARY SUN GEAR AND ONE-WAY CLUTCH
The primary sun gear is the center gear in a planetary gear set. A one-way clutch allows rotation in only one direction. The one-way clutch on the primary sun gear is a "sprag" clutch. If the clutch tries to rotate in the wrong direction, the sprag become wedged between the inner and outer races and rotation is stopped.

ONE-WAY CLUTCH AND FRONT PLANET
The one-way clutch on the front planet is a "roller" clutch. The one-way clutch allows rotation in one direction only. If the clutch tries to rotate in the wrong direction, the rollers are forced into their slots and the outer race is secured to the inner race.