This thesis activity is focused on the investigation of integrated e-Axle solutions, also called 3in1 for electrified vehicles (EVs and HEVs). This modular element is made of the reversible electric motor, the mechanical transmission and the bidirectional DC/AC converter, also called inverter. The investigation starts with a brief description of the components of the e-Axle, followed by the state of the art analysis both for passenger cars and heavy duty vehicles. Following on, the transmission design is described both for single-speed and two-speeds arrangement. The same is for the e-motors related to the two speeds transmission solutions for a small Class A passenger car.