A vehicle powertrain system and powertrain actuator therefor is provided. The powertrain actuator selectively couples a first rotatable member to a second rotatable member to transfer torque therebetween and selectively decouples the first rotatable member from the second rotatable member to prevent the transfer of torque therebetween. The powertrain actuator includes a tubular cam assembly having a tubular first member and a tubular second member. The tubular first and second tubular members have end surfaces that interact with one another upon energizing a unidirectional solenoid. Upon a first energization of the solenoid, the first and second tubular members interact to operably couple the first and second rotatable members to allow torque to be transferred therebetween, and upon a second energization of the solenoid, the first and second tubular members interact to selectively decouple the first the second rotatable members to prevent the transfer of torque therebetween.