A motorized wheel hub assembly includes a sealed motor section having first and second coaxial shafts extending from the motor section, the second shaft being a rotary shaft and a gear reduction section adjacent to the motor section, the gear reduction section including a pinion at the end of the rotary shaft, a plurality of planet gears rotatably mounted to the housing in meshing engagement with the pinion and a third shaft connected to the motor housing, all of the shafts being separate but coaxial. A hub having an interior surface closely surrounds the motor and gear reduction sections and is rotatably coupled to the first and third shafts. A ring gear formed in the interior surface of the hub is in meshing engagement with the planet gears so that when the second shaft rotates at a selected speed, the hub rotates relative to the first and third shafts at a lesser speed. Preferably, the hub is partially filled with oil to conduct heat from the motor section to the outside.