Constant velocity universal joint

An improved constant velocity universal joint having an outer member and an inner member each mounted through a ball cage having a plurality of balls mounted in respective ball windows, said balls being in engagement with respective pairs of longitudinally extending ball grooves formed in mutually facing spherical surfaces of the respective inner and outer members, said ball cage having front and rear edges and being inserted front edge first into said outer member, the improvement wherein the ball cage has an outer spherical surface in contact with the spherical inner surface of the outer member and is provided with respective longitudinally extending cut-out grooves continuing from each of the respective ball windows, said cut-out grooves being relatively small in size with contours substantially conforming to respective partition walls disposed between respective adjacent ball grooves in said outer member, said ball windows having front and rear edge portions, said cut-out grooves each being provided only at one said rear edge portion of each of said ball windows and extending longitudinally towards the rear edge of said ball cage, and each partition wall of the outer member is insertable in each cut-out groove.