Three methods of fabricating an intermediate, center or combination gear for a stacked planetary gear assembly are presented. A first method comprehends forming male splines on the outer surface of the inner (ring) gear and female splines on the inner surface of the outer (sun) gear. The gears are then heat treated and assembled. A second method comprehends broaching internal splines in the outer (sun) gear as well as end milling, broaching or polygon turning face splines on one end of the outer gear and an opposing, adjacent end of the inner (ring) gear. A third method includes fabricating and heat treating the inner and outer gears. A small area of the hardened case is then removed by, for example, machining. The gears are mated, heated rapidly by a pulse of electric current and upset in the heated region.