A vehicle drivetrain assembly (10) and method for making the assembly of first and second torque transmitting members (12, 14), one of which (12) is aluminum and the other of which (14) is steel, that are joined by an electromagnetic pulse weld (16) progressively applied along a radial direction relative to the axis (A) of assembly rotation so as to provide a lightweight construction.

A ring gear assembly includes a ring gear, a gear box case, and a set of bolts. The ring gear includes a set of gear teeth inside the ring gear and arranged in a circle around the ring gear axis. The ring gear further includes a set of flanges arranged along at least one side of the ring gear. Each flange has a respective flange bolt hole therethrough, and each flange bolt hole has a respective bolt axis that is oriented perpendicular to the ring gear axis. The gear box case has a set of gear box bolt holes therethrough, each gear box bolt hole corresponding to a respective one of the flange bolt holes. Each of the bolts passes through a respective one of the gear box bolt holes and its corresponding flange bolt hole to fasten the ring gear to the gear box case.

A differential assembly includes a first case rotatable about an axis and defining a first mounting flange having a through hole and a second case abutting the first case to define a gear nest cavity therebetween. The second case further defines a second mounting flange having a through hole and formed to mate to the first mounting flange. The differential assembly also includes a ring gear mounted to the first mounting flange and fastener extending through the through hole of both the first mounting flange and second mounting flange into a fastener hole of the ring gear. Additionally, the first mounting flange is sandwiched between the second mounting flange and the ring gear.

A differential hypoid gear, a pinion gear, and paired hypoid gears formed by a combination thereof are provided. The differential hypoid gear includes a ring-shaped main body and a tooth-forming surface, and has a chemical component composition including C: 0.15-0.30 mass %, Si: 0.55-1.00 mass %, Mn: 0.50-1.20 mass %, Cr: 0.50-1.50 mass %, Al: 0.020-0.080 mass %, B: 0.0005-0.0050 mass %, Ti: 0.01-0.08 mass %, N: 0.0020-0.0100 mass %, Mo: 0.25 mass % or less, and Nb: less than 0.10 mass %, the remainder being Fe and unavoidable impurities. The chemical component composition satisfies Formulae 1 and 2. The differential hypoid gear has a metallographic structure including mainly tempered martensite. A martensite ratio at an inside of a dedendum differs between an end portion of a tooth and a central portion of the tooth within a range of 15% or less. A core hardness of the dedendum at the central portion falls within 350-500 HV.

A gear for use in a transmission system. The gear comprises an outer annular element having gear teeth on a radially outer surface thereof and an inner support element arranged coaxially with the outer annular element. The gear further comprises first and second opposing side walls, each side wall extending from the outer annular element to the inner support element to form an annular space. At least one of the first and second side walls extends from the outer annular element at an angle greater than 0 degrees with respect to a direction perpendicular to the rotational axis of the gear.

A power transmission device has a hub portion of a ring gear is fixed by a weld portion to a flange portion on an outer periphery of a transmission member, an annular groove that is recessed in the inner side of the axial direction is formed in a side face of the hub portion for making axial positions of the annular groove and the cavity part partially coincide with each other, the hub portion is narrowed partway along a part sandwiched between the cavity part and weld portion and the annular groove when viewed in a cross section transecting the annular groove, and a narrowed portion is set to have a thickness that alleviates residual stress produced around the weld portion of the flange portion by the force with which the flange portion and the hub portion pull each other in response to thermal shrinkage of the weld portion.

A differential hypoid gear, a pinion gear, and paired hypoid gears formed by a combination thereof are provided. The differential hypoid gear includes a ring-shaped main body and a tooth-forming surface, and has a chemical component composition including C: 0.15-0.30 mass %, Si: 0.55-1.00 mass %, Mn: 0.50-1.20 mass %, Cr: 0.50-1.50 mass %, Al: 0.020-0.080 mass %, B: 0.0005-0.0050 mass %, Ti: 0.01-0.08 mass %, N: 0.0020-0.0100 mass %, Mo: 0.25 mass % or less, and Nb: less than 0.10 mass %, the remainder being Fe and unavoidable impurities. The chemical component composition satisfies Formulae 1 and 2. The differential hypoid gear has a metallographic structure including mainly tempered martensite. A martensite ratio at an inside of a dedendum differs between an end portion of a tooth and a central portion of the tooth within a range of 15% or less. A core hardness of the dedendum at the central portion falls within 350-500 HV.

A pinion shaft assembly facilitates assembly of an automotive differential. An angular contact double row ball bearing is assembled to an outer surface of a hollow pinion shaft. An axial pre-load is established and maintained by orbitally forming an outwardly turned portion of the hollow pinion shaft. In some embodiments, the two inner rings are assembled to the pinion shaft. In other embodiments, a raceway may be formed directly on an outer surface of the pinion shaft to eliminate one of the inner rings. The pinion shaft includes a spline, such as an axial spline or a face spline, for fixation to a driveshaft.

A vehicle differential device includes a plurality of pinion gear sets. Each of the pinion gear sets includes a first pinion gear configured to mesh with a first outer helical gear and a plurality of second pinion gears configured to mesh with a second outer helical gear. The first pinion gear integrally includes an axially one end side gear portion configured to mesh with the first outer helical gear and an axially other end side gear portion configured to mesh with the second pinion gears. The second pinion gears are configured to mesh with the second outer helical gear at positions separated from each other in a circumferential direction of the second outer helical gear, and the axially other end side gear portion of the first pinion gear is configured to mesh with the second pinion gears at positions radially outward of the second outer helical gear.

An axle assembly with a carrier housing, an input pinion and a ring gear. The input pinion includes pinion gear teeth and is supported for rotation about a first axis relative to the carrier housing via first and second bearings that are disposed along the first axis on opposite sides of the pinion gear teeth. The ring gear includes ring gear teeth that are meshed to the pinion gear teeth and a third bearing supports the ring gear for rotation about the second axis relative to the carrier housing. The third bearing is disposed along the second axis on a side of the ring gear that is opposite the first axis.