In OLDER Ford power steering pumps I found that Royal Purple ATF severely quieted the whining noise, a notorious trademark of Ford PS pumps. WELL I changed the fluid in the Expedition with M1 ATF. Then did it again a few weeks later. Then a few weeks later, I did my sister's Explorer pump with Royal Purple and did the Expedition as well. BIG MISTAKE. It got LOUD (Expedition, Explorer got quieter) REALLY loud. Previously it made no noise. Flushed with M1 ATF. Got a bit quieter. Have performed this three times now and the noise is close to gone. So there is obviously a notable difference between the early and current pumps.