Differential gearing for vehicle including planetary gear mechanism and method of manufacturing same

A sun gear 6 is rotatably fitted on a circle which is located on the inside of and concentric with an internal gear 4. A plurality of planet gears 8 carried by a planetary carrier 10 are disposed between the internal gear 4 and the sun gear 6 in meshing engagement with the internal gear 4 and the sun gear 6. In operation, a frictional resistance between a tooth crest 8a of the planet gear 8 and a planet gear carrying space in the planetary carrier 10 effects a differential action limitation. The tooth crest 8a of the planet gear 8 is formed with a number of fine recesses in an irregular condition. Because the recesses are not in the form of continuous grooves, but are in the form of pockets, a lubricant oil can kept in place reliably. Accordingly, the abrasion resistance and the seizure resistance of the planet gears 8 and the planetary carrier 10 are improved while allowing noises and vibrations to be reduced.