A shift assembly for a two-speed transfer case utilizes a single actuator
to drive both the speed range selection mechanism and a modulating
friction clutch pack which selectively transfers drive torque from a
primary output to a secondary output. The shift assembly includes an
actuator which rotates a shift rail and cam having an intermediate helical
track and a dwell region at each end. A lost motion assembly operating in
conjunction with the helical cam selectively engages and disengages the
clutch when the cam follower is in one of the two dwell regions. Thus, the
shift assembly provides sequential operation from full clutch engagement
in a first speed range, clutch disengagement in the first speed range,
de-selection of the first speed range, selection, and de-selection of
neutral, selection of a second speed range and, up to full engagement of
the clutch in the second speed range.
