driveline assembly 16 as will be detailed compounder assembly 24 also includes torque transfer devices that are controlled by an electro hydraulic shift control system 28 for establishing either of a direct drive connection or a ratio drive connection between the output shaft of transmission 20 and driveshaft 26 in order to coordinate shifting of the torque transfer devices in transmission 20 and compounder assembly 24 a transmission controller 30 is provided which selectively controls actuation of transmission shift control system 22 and compounder shift control system 28 in response to signals from various vehicle sensors 32 the signals from vehicle sensors 32 are inputted to controller 30 and used to develop control signals that are delivered to the shift system actuators for establishing the desired gear ratio drive connection between engine 18 and driveshaft 26 with reference to fig2 the components associated with compounder assembly 24 will now be described in greater detail compounder assembly 24 includes an underdrive unit 34 which is operable to selectively interconnect an input shaft 36 and an output shaft 38 for establishing both of the direct and ratio drive connections therebetween input shaft 38 and output shaft 38 are rotatably supported within a housing 40 and are coaxially aligned such that they rotate about a common longitudinal axis u201c a u201d while not shown it is understood that input shaft 36 is adapted for connection to and rotation with the output shaft of transmission 20 likewise output shaft 38 is adapted for connection to and rotation with driveshaft 26 of driveline assembly 16 underdrive unit 34 includes a planetary gearset 42 having an input member driven by input shaft 36 a reaction member.