A driveline 10 for a vehicle comprising an engine 11 connected to an input of a transmission 14 via a one-way sprag clutch 13, a launch clutch 16, and a torque converter or other launch facility being provided for the transmission. The one-way sprag clutch only delivers power to the transmission when the input speed from the engine equals or exceeds the input speed from the transmission. The launch clutch may be a centrifugal clutch, and the sprag clutch may be incorporated in the launch clutch. A twin mass flywheel 12 to dampen torsional vibrations could be included, in which the sprag clutch could be incorporated. A starter motor 20 for the engine is also included. The driveline could be for a hybrid vehicle, and therefore include an electric power unit (27, Fig.5). The electric power unit may be capable of launching the vehicle. A regenerating overrunning mode is also available. The transmission could be automatic or manual, or have a twin clutch.
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