1. A method for controlling a powertrain system comprising an internal combustion engine, a multi-mode transmission and a driveline, the method comprising: in response to a command to execute an engine autostart operation during vehicle operation: executing a clutch-driven engine autostart operation to start the engine upon determining a present transmission output speed is greater than a minimum output speed for engine operation and upon determining a selected clutch configured to effect a mechanical coupling between the engine and the driveline is activatable; wherein executing the clutch-driven autostart operation includes: activating an input damper; disabling engine speed control; activating the selected clutch; and fueling and firing the engine when engine speed exceeds a threshold speed.