An electric drive unit that includes an electric motor having a rotor with a rotor shaft and a heat exchanger that is received in the rotor shaft. The heat exchanger has a plurality of heat exchanger plates, each of which having a hub, a rim member, and disc spring portion that interconnects the hub and the rib member. Each disk spring portion defines a plurality of coolant apertures. The heat exchanger plates are press-fit to the rotor shaft such that each disc spring portion is deflected from a pre-installation state, and each rim member is engaged to an interior surface of the rotor shaft while being spaced apart from adjacent rim members along a rotational axis of the rotor. A first coolant passage is disposed through the hubs of the plates. The coolant apertures in the heat exchanger plates cooperate to form a plurality of second coolant passages.