Abstract: A shaft member of an embodiment includes: a base material having a shaft shape and made of steel; a low phosphorus plating layer that is laminated on the base material, that includes phosphorus, and in which the phosphorus content is 4.5 mass % or less; and a base plating layer that is formed as an electrolytic nickel phosphorus plating layer or a high phosphorus plating layer laminated between the base material and the low phosphorus plating layer. It is thus possible to increase the strength of the shaft member and decrease the size of the shaft member.

Abstract: A differential device includes: a differential case; a plurality of pinion shafts supported by the differential case and that is disposed on a first axis and a second axis orthogonal to the first axis; a first pinion gear and a second pinion gear that are each rotatably supported by the plurality of pinion shafts and that are disposed on the first axis, and a third pinion gear and a fourth pinion gear that are each rotatably supported by the plurality of pinion shafts and that are disposed on the second axis; and a first side gear and a second side gear that mesh with the first to fourth pinion gears and that are preloaded toward the first to fourth pinion gears. The number of teeth of the first side gear and second side gear is configured to be the 4N+2 in which N is an integer.

Abstract: A shaft member of an embodiment includes: a base material having a shaft shape and made of steel; a low phosphorus plating layer that is laminated on the base material, that includes phosphorus, and in which the phosphorus content is 4.5 mass % or less; and a base plating layer that is formed as an electrolytic nickel phosphorus plating layer or a high phosphorus plating layer laminated between the base material and the low phosphorus plating layer. It is thus possible to increase the strength of the shaft member and decrease the size of the shaft member.

Abstract: A differential case has no hole other than two oil holes except for a pinion shaft hole and a pair of drive shaft holes and has an annular receiver attached thereto that has an inner periphery smaller than the outer periphery of side gear washers with respect to the rotation center of the rotation axis of drive shafts and that has an outer periphery located beyond the outermost edge of the oil holes with respect to the rotation center of the rotation axis. This controls the outflow of lubricating oil located radially outward of the inner periphery of the receiver, thus allowing the side gear washers to be supplied with lubricating oil, regardless of whether the differential case is rotating or stops rotating.

Abstract: A differential case has no hole other than two oil holes except for a pinion shaft hole and a pair of drive shaft holes and has an annular receiver attached thereto that has an inner periphery smaller than the outer periphery of side gear washers with respect to the rotation center of the rotation axis of drive shafts and that has an outer periphery located beyond the outermost edge of the oil holes with respect to the rotation center of the rotation axis. This controls the outflow of lubricating oil located radially outward of the inner periphery of the receiver, thus allowing the side gear washers to be supplied with lubricating oil, regardless of whether the differential case is rotating or stops rotating.