The present invention relates to a torsional damper for an electrically-variable transmission. The torsional damper is equipped with a hydraulically actuable lock-out clutch to directly couple the engine to the input shaft of the transmission. The electric motors provided with the electrically-variable transmission can serve to effectively cancel out engine compression pulses when the springs of the torsional damper are locked out. When the engine is off and the torsional damper assembly is in use, an auxiliary pump is provided to pump oil to the torsional damper assembly. The lock-out clutch is hydraulically balanced by the oil supplied by the auxiliary pump. The pump is strategically mounted to the transmission housing in a manner to minimize the distance between the auxiliary pump and the transmission without affecting any vehicle ground clearance requirements.