A secondary drive unit for an all wheel drive vehicle having left and right secondary drive wheels which are selectively connected to a drive source through the secondary drive unit, the secondary drive unit housing a main shaft operatively coupled to the drive source, the secondary drive unit comprising: a secondary drive unit housing, the housing defining a first section for receiving the main shaft, and the housing defining a second section for enclosing a twin clutch assembly, a left output shaft concentric with the main shaft, the left output shaft for transferring torque to the left secondary drive wheel; a right output shaft coaxial with the left output shaft, the right output shaft for transferring torque to the right secondary drive wheel; the twin clutch assembly having: a clutch housing connected to the main shaft, a left clutch for selectively connecting the left output shaft and the clutch housing, a right clutch for selectively connecting the right output shaft and the clutch housing, and a rigid center plate extending from an inner wall of the clutch housing, the rigid center plate separating the left and right clutches (312, 314), characterized in that: one of the right or left clutches (312, 314) further comprises a dual action piston assembly, the dual action piston assembly comprising: a dual action piston, a cavity defined in a first inward facing wall of the SDU housing for receiving the dual action piston, and first and second ports defined in the SDU housing for passing fluid to activate the dual action piston assembly, the dual action piston and the cavity in the first inward facing wall defining first and second chambers (CH1, CH2) for receiving fluid through the first and second ports, the first chamber having a volume less than a volume of the second chamber. a secondary drive unit housing, the housing defining a first section for receiving the main shaft, and the housing defining a second section for enclosing a twin clutch assembly, a left output shaft concentric with the main shaft, the left output shaft for transferring torque to the left secondary drive wheel; a right output shaft coaxial with the left output shaft, the right output shaft for transferring torque to the right secondary drive wheel; the twin clutch assembly having: a clutch housing connected to the main shaft, a left clutch for selectively connecting the left output shaft and the clutch housing, a right clutch for selectively connecting the right output shaft and the clutch housing, and a rigid center plate extending from an inner wall of the clutch housing, the rigid center plate separating the left and right clutches (312, 314), characterized in that: one of the right or left clutches (312, 314) further comprises a dual action piston assembly, the dual action piston assembly comprising: a dual action piston, a cavity defined in a first inward facing wall of the SDU housing for receiving the dual action piston, and first and second ports defined in the SDU housing for passing fluid to activate the dual action piston assembly, the dual action piston and the cavity in the first inward facing wall defining first and second chambers (CH1, CH2) for receiving fluid through the first and second ports, the first chamber having a volume less than a volume of the second chamber. a clutch housing connected to the main shaft, a left clutch for selectively connecting the left output shaft and the clutch housing, a right clutch for selectively connecting the right output shaft and the clutch housing, and a rigid center plate extending from an inner wall of the clutch housing, the rigid center plate separating the left and right clutches (312, 314), characterized in that: one of the right or left clutches (312, 314) further comprises a dual action piston assembly, the dual action piston assembly comprising: a dual action piston, a cavity defined in a first inward facing wall of the SDU housing for receiving the dual action piston, and first and second ports defined in the SDU housing for passing fluid to activate the dual action piston assembly, the dual action piston and the cavity in the first inward facing wall defining first and second chambers (CH1, CH2) for receiving fluid through the first and second ports, the first chamber having a volume less than a volume of the second chamber. a dual action piston, a cavity defined in a first inward facing wall of the SDU housing for receiving the dual action piston, and first and second ports defined in the SDU housing for passing fluid to activate the dual action piston assembly, the dual action piston and the cavity in the first inward facing wall defining first and second chambers (CH1, CH2) for receiving fluid through the first and second ports, the first chamber having a volume less than a volume of the second chamber.