Patent ID: 7882919

Claim:
A shaft drive device where a shaft of a pinion gear engaged with a ring gear extends toward a power unit in a final gear case that is provided in a power transmission system between the power unit and a wheel, the shaft device comprising: a first spline provided on an outer circumference of the shaft; a second spline is provided on an inner circumference of a cylindrical portion of a pinion joint that forms a receiving portion of a joint provided at a rear end of a drive shaft for transmitting power from the power unit to the pinion gear, the second spline of the pinion joint and the first spline of the pinion gear being engaged with each other so that the pinion gear is spline-connected to the pinion joint; a hole formed at the shaft of the pinion gear in an axial direction thereof; a threaded portion formed at a lower portion of the hole, wherein the pinion joint is fixed to the pinion gear by a bolt that is threadedly engaged with the threaded portion of the hole, and wherein a flexible portion is formed between a head portion of the bolt and a threaded portion of the bolt.