A portable power take-off unit for mounting to and dismounting from the rear of a vehicle, such as a pickup truck, providing mechanical operational power to construction and farm implements and machinery includes an engine for driving a belt and pulley assembly that drives a chain and sprocket assembly that, in turn, drives a power take-off shaft at selectable high or low speeds. An elongated drive shaft from the machinery is connected to the power take-off shaft for connection to the implement or machinery so that power can be provided thereto. The power take-off unit includes a hydraulic system, comprising a pump, reservoir, couplers, and hoses, for controlling the operation of the machinery, and a manually operable engagement lever for engaging and disengaging the belt and pulley system thereby controlling the engagement and disengagement of the power take-off shaft.