Hydraulically actuated transfer case

A drive torque transfer case for a vehicle having a transmission, comprising:

• an input shaft extending along a longitudinal axis A;
• an output shaft co-axially aligned with the input shaft;
• a gear assembly coupled to the input shaft;
• a range clutch assembly coupled to the output shaft, wherein the range clutch assembly includes a clutch member and a multi-piston actuator configured to receive a pressurized transmission fluid from the transmission for selectively axially translating the clutch member to engage a component of the gear assembly for transmitting a drive torque from the input shaft to the output shaft;
• and
• a transfer case housing;
• wherein the gear assembly includes a sun gear rotationally fixed to the input shaft, a ring gear non-rotationally fixed to the transfer case housing, and planetary gear carrier having a plurality of planetary gears meshed between the sun gear and the ring gear;
• wherein the clutch member is a dog clutch splined to the output shaft and axially translatable in a first axial direction and in an opposite second axial direction;
• wherein the multi-piston actuator is configured to selectively axially translate the dog clutch into a first position, a second position, and a third position;
• and
• wherein the first position is in engagement with the sun gear, the second positon is engagement with the planetary carrier, and the third position is in a neutral position;
• and
• wherein the multi-piston actuator comprises:
• a piston housing defined by a portion of an interior surface of the transfer case housing;
• an internal piston disposed within the piston housing, wherein the internal piston is axially slideable within the piston housing;
• and
• an external piston disposed within the piston housing, wherein the external piston is axially slideable against a surface of the internal piston;
• wherein the external piston includes an exterior surface defining a shift fork in engagement with the dog clutch, and
• wherein the internal piston co-operates with the external piston to selectively axially translate the dog clutch into the first position, the second position, and the third position.