A retaining pin assembly for a lifting system which includes a hook prong and a hook cam. The retaining pin assembly includes at least one lock arm assembly having a first end with at least one aperture which aligns with an opening through the hook cam and having an opposed second end with at least one aperture which aligns with an opening through the hook prong. A hook cam retaining pin has a head and has a shaft passing through the hook cam opening and the lock arm first end aperture, wherein the shaft has at least one groove therein parallel to the axis of the shaft. A retaining ring surrounds the hook cam shaft, the retaining ring having at least one inwardly extending tab received in the shaft groove in order to retain the pin in the lock arm. A recess in the lock arm receives the retaining ring therein.