An improved twin clutch, two-speed disconnect secondary drive unit, which may be configured as a rear drive unit (RDU) for an all wheel drive vehicle is provided. The RDU is driven through an input shaft, which is connected to a vehicle drive source such as a motor, and includes a twin clutch assembly, which is connected to the drive shaft and is selectively actuated to drive left and right main shafts, which drive respective wheels of the vehicle. The RDU further includes a modular a shift assembly mountable to one or both of said main shafts to drive output shafts, wherein each shift assembly is selectively operable between the hi-range and lo-range modes to shift driving operation of the output shafts between hi-speed and lo-speed operation. The shift assembly may be controlled by improved mono-stable or bi-stable actuators.