Transition between the electric drive and a parallel driving in a hybrid electric vehicle powertrain

A method of operating a vehicle drive train comprising the driving of first wheels using an electric motor, the starting of an engine, the use of a second electric motor which is driven by the engine to a synchronous speed at an input of a transmission with a desired engaged gear to produce the engagement of a clutch which connects the input and the machine, and using the engine and the transmission for driving second wheels.