A park-position mechanism includes a selector mechanism that includes a cam mounted on a selector hub shaft, a park gear mounted on a main shaft and corresponding in position to the cam, a park arm arranged between the cam and the park gear. The park arm has a holed base fit over a stud that rotates and supports the park arm in a crankshaft case. A torsion spring is arranged between the park arm and the crankshaft case with ends attached to the park arm and the crankshaft case respectively. The park arm has a driven section and an engaging section respectively extending from opposite sides of the holed base. The engaging section forms a projection. The driven section forms a hole in which a guide rod is received in an axially movable manner. The guide rod is engaged with the earn and is thus selectively driven by the cam to cause engagement of the projection of the engaging section with the park gear. A resilient member is arranged between the hole and the guide rod. The resilient member and the guide rod function to absorb a driving force induced by the earn to eliminate direct application of the force on the driven section thereby protecting the park arm from being damaged by excessive amount of force acting thereon and enhancing operation smooth of switching to the PARK position.