Plastic movable guide for transmission device

In a power transmission comprising a flexible traveling power transmission medium, the combination of a tensioner plunger having a guide-engaging end surface, and a plastic movable guide comprising an elongated guide body composed of an elongated shoe having a front surface for sliding contact with the power transmission medium and a back side, and a plate-receiving portion extending longitudinally along the back side of said shoe and having a longitudinally extending slot having an opening facing in a direction opposite to the direction in which said front surface of the shoe faces, the shoe and plate-receiving portion being integrally molded as a unit from a synthetic resin, and a reinforcing plate fitting into said slot, the guide body and reinforcing plate being pivotable about a mounting located adjacent one end of the guide body, wherein a part of said plate-receiving portion remote from said one end of the guide body forms a plunger-engaging surface engaged with said end surface of said plunger, the plunger-engaging surface being divided by the opening of said slot, and said reinforcing plate being recessed in said slot, at least at the location at which the slot divides said plunger-engaging surface, so that said reinforcing plate does not protrude from the part of the opening of said slot dividing the plunger-engaging surface, whereby the plunger is prevented from direct contact with the reinforcing plate.