Propeller shaft and constant velocity universal joint for a propeller shaft

A constant velocity universal joint for a propeller shaft having a shaft portion, comprising:

• an outer joint member in which eight guide grooves extending in an axial direction are formed on an inner spherical surface thereof;
• an inner joint member in which eight guide grooves extending in the axial direction are formed on an outer spherical surface thereof and an engagement portion having teeth which come into tooth-engagement with the shaft portion of the propeller shaft is formed on an inner surface thereof;
• eight torque transmitting balls disposed in eight ball tracks, respectively, each ball track formed by cooperation between one of the guide grooves in the outer joint member and a corresponding one of the guide grooves in the inner joint member;
• and a cage for holding each one of the torque transmitting balls,
• wherein the ball tracks widened toward one side in the axial direction forming wedge shape configurations, and
• a ratio Rw (=W/PCDSERR) between an axial width (W) in the axial direction of the inner joint member and a pitch circle diameter (PCDSERR) of the teeth of the engagement portion is 0.57<Rw≦0.95 and a circumferential width (L) in the circumferential direction of the outer surface between the guide grooves of the inner joint member is L≦3.5 mm.