A hydraulic pump assembly includes an electric motor; a hydraulic pump driveably connected to the electric motor via a rotatable coupling; wherein the rotatable coupling includes a splined connection housed within a chamber comprising a chamber wall, wherein the chamber defines a flow passage for hydraulic oil for lubricating the rotatable coupling, the chamber includes an inlet for receiving a flow of hydraulic oil from the pump and an outlet for exiting the flow of hydraulic oil to the exterior of the chamber.