Abstract: A new planetary reduction gear assembly for reducing output speed of an agricultural tractor. The inventive device includes an input shaft having an inner portion and an outer portion. The inner portion has a female coupling collar disposed thereon. The female coupling collar is dimensioned for coupling with an outboard shaft of a power take off shaft of a tractor. A gear system is coupled with the outer portion of the input shaft. The gear system includes a central gear coupled with the outer portion of the input shaft. The central gear has three planetary gears engaged thereto. The casing has a rear face, a front face and an outer periphery. The outer periphery has teeth disposed circumferentially on an interior surface thereof. The teeth engage the three planetary gears. The three planetary gears have shafts extending outwardly from central axles thereof. Free ends of the shafts couple with a planetary gear carrier. An output shaft is provided having an inner portion and an outer portion.