Transmission shift mechanism

A shift mechanism for a transmission comprising first and second rotary members mounted for rotation adjacent to one another about a common axis, said rotary members having external splines around outer peripheries corresponding in numbers and dimensions, a shift collar having internal splines around an inner circumference mounted with its internal splines in mesh with the external splines of one of said rotary members, said shift collar being shiftable axially to a position so that its internal splines are also in mesh with the external splines of the other rotary member to provide corotation of said rotary members, and engagement means for synchronizing rotation of said other rotary member with said shift collar for uniform corotation during initial axial movement of said shift collar and thereafter for guiding the splines of said shift collar into the external splines of said other rotary member during further axial movement of said shift collar, said engagement means including a plurality of circumferentially spaced blocking members on one of the parts to be synchronized axially directed toward the other of the parts to be synchronized, each blocking member having uniform transverse dimensions throughout its length, and a plurality of circumferentially spaced cam members on the other of the synchronized parts axially directed toward said one synchronized part, each of said cam members having a surface inclined circumferentially away from said one part and terminating in a trailing edge spaced from the leading edge of the next adjacent cam member, and leading and trailing surfaces extending longitudinally from its leading and trailing edges to provide an axial slot of uniform transverse cross section throughout its length and of a dimension sufficient to accommodate a blocking member of said one part, the splines of said shift collar and said one rotary member being in alignment with one another for meshing when said blocking member is in axial alignment with said slot.