A power transfer unit for use in a vehicle for transferring a torque, the power transfer unit comprising: a first shaft configured to receive the torque from a vehicle differential assembly; a second shaft configured to output the torque to a second device (43, 29); and an activating assembly for selectively transferring the torque from the first shaft to the second shaft, the activating assembly including: a sliding cam; a rotating cam; an actuator configured to selectively rotate the rotating cam relative to the sliding cam; an engaging gear; wherein the engaging gear is configured to be moved by the sliding cam between a first engaged position where the torque is transferred from the first shaft to the second shaft through the engaging gear and a second disengaged position where no torque is transferred to the second shaft 36); wherein relative rotation between the rotating cam and the sliding cam moves the sliding cam thereby moving the engaging gear between the first engaged and second disengaged positions; characterized in that the activating assembly further includes a guide member configured to be driven by the sliding cam to move the engaging gear between the first engaged and second disengaged positions, one end of the guide member surrounds at least a portion of the engaging gear and the other end of the guide member abuts the sliding cam; wherein, when the guide member moves with the sliding cam toward the rotating cam, the guide member pulls the engaging gear to the first engaged position and into engagement with the first shaft. a first shaft configured to receive the torque from a vehicle differential assembly; a second shaft configured to output the torque to a second device (43, 29); and an activating assembly for selectively transferring the torque from the first shaft to the second shaft, the activating assembly including: a sliding cam; a rotating cam; an actuator configured to selectively rotate the rotating cam relative to the sliding cam; an engaging gear; wherein the engaging gear is configured to be moved by the sliding cam between a first engaged position where the torque is transferred from the first shaft to the second shaft through the engaging gear and a second disengaged position where no torque is transferred to the second shaft 36); wherein relative rotation between the rotating cam and the sliding cam moves the sliding cam thereby moving the engaging gear between the first engaged and second disengaged positions; characterized in that the activating assembly further includes a guide member configured to be driven by the sliding cam to move the engaging gear between the first engaged and second disengaged positions, one end of the guide member surrounds at least a portion of the engaging gear and the other end of the guide member abuts the sliding cam; wherein, when the guide member moves with the sliding cam toward the rotating cam, the guide member pulls the engaging gear to the first engaged position and into engagement with the first shaft. a sliding cam; a rotating cam; an actuator configured to selectively rotate the rotating cam relative to the sliding cam; an engaging gear; wherein the engaging gear is configured to be moved by the sliding cam between a first engaged position where the torque is transferred from the first shaft to the second shaft through the engaging gear and a second disengaged position where no torque is transferred to the second shaft 36); wherein relative rotation between the rotating cam and the sliding cam moves the sliding cam thereby moving the engaging gear between the first engaged and second disengaged positions; characterized in that the activating assembly further includes a guide member configured to be driven by the sliding cam to move the engaging gear between the first engaged and second disengaged positions, one end of the guide member surrounds at least a portion of the engaging gear and the other end of the guide member abuts the sliding cam; wherein, when the guide member moves with the sliding cam toward the rotating cam, the guide member pulls the engaging gear to the first engaged position and into engagement with the first shaft.