A speed select shift mechanism for a belt drive assembly to be installed on a shaft capable of shifting between high, low and neutral speeds is disclosed. The shift mechanism includes a shift collar that is enclosed within an enclosure to prevent debris from contacting the inner operations of the shift mechanism and thereby reduce wear and tear of the shift mechanism along with down time for maintenance of the device. The shift mechanism includes a shaft, a first pulley, a shift collar, a second pulley and a shifter. The shift collar further includes dowels that cooperatively engage corresponding apertures on the pulleys.