An automatic slack adjuster one-way clutch includes a first part, which is rotatable about an axis in both a drive direction and a slip direction opposite to the drive direction, and a second part, which is driven about the axis by the first part only when the first part rotates in the drive direction. The second part is not driven by the first part when the first part rotates in the slip direction. Multiple movable teeth, carried by one of the parts, are displaceable axially relative to both of the parts and engage between teeth immovably fixed on the other of the parts. The first part may be either an input part or an output part of the clutch.