A holddown pin mechanism for hydraulic power units is a ball guide with a cylindrical flat base having a central opening, a plurality of spaced elongated holddown pins have one end rigidly secured to one side of said ball guide. The pins extend outwardly at right angles from the side of said washer to which they are secured. The holddown pin mechanism is placed in a hydraulic cylinder block having a center bore, with the pins extending into holes in the block. A flat washer on a shaft extending through the block engages the free ends of the pins.