Does this describe what you feel. If your turning the wheel slowly to the right and then back to the left quickly do you feel a "dead" spot or a breif lack of power assist? If you feel this symtom that is air traped in the gearbox and will drive out. This system creates its pressure based on volume, if you are loosing volume due to an internal (bypassing back to the return) leak most the time it is described as a whine or viabration from the pump, not a pulse. I hate to see you replace the gearbox and be in the same boat. I'm happy to answer any questions you may have, if you like give me a call. 702.734.8090

Chris