A method of shifting a power distribution unit for a vehicle from a first operating state to a second operating state is provided. The method includes the step of adjusting a rotational speed of a portion of a second axle assembly using a clutching device to impart energy to a lubricant within the second axle assembly. A controller in communication with a power source of the vehicle adjusts an operating condition of the power source to facilitate moving the clutching device. The power distribution unit includes an inter-axle differential capable being placed in a locked condition by the clutching device and of accommodating a rotational difference between a first output gear and a second output gear with the inter-axle differential.