Method for assembling power transfer apparatus

A method for assembling a power transfer apparatus for selectively changing the speed of output shaft relative to the speed of an input shaft, the method comprising:

• assembling an oil pump driving pin to the output shaft;
• assembling an oil pump sub-assembly including a pump base, a pump body having an inner rotor and an outer rotor, and a pump cover in such a manner that the inner rotor fits on the oil pump driving pin;
• assembling a planetary carrier sub-assembly onto the pump cover of the oil pump sub-assembly, wherein the planetary carrier sub-assembly includes a planetary carrier, a first pinion gear rotatably carried on the planetary carrier, a second pinion gear formed with the first pinion gear and having the number of teeth which is different from that of the first pinion gear, a first sun gear meshing with the first pinion gear and a second sun gear meshing with the second pinion gear;
• assembling a clutch sub-assembly onto the planetary carrier, wherein the clutch sub-assembly includes a clutch inner hub, a clutch guide, a plurality of clutch discs mounted on the clutch inner hub, a plurality of clutch plates mounted on the clutch guide so as to be disposed alternatively with the clutch discs and a clutch piston and biasing unit for biasing the clutch piston in a direction in which the clutch discs and the clutch plates are brought into engagement with each other;
• assembling a transmission brake onto the clutch sub-assembly in such a manner that a brake inner hub is coupled with the clutch piston, wherein the transmission brake includes the brake inner hub, a plurality of brake discs and a plurality of brake plates;
• inserting the input shaft so as to fit in the first sun gear at a first spline and the clutch sub-assembly at a second spline, respectively;
• and
• assembling a front case sub-assembly onto said input shaft, said front case sub-assembly having bearings therein for rotatably bearing the input shafts and an actuator for actuating the transmission brake, wherein said front case sub-assembly is thereby mounted to a differential.