I have replaced the pump twice on my 2006 5.4L. Both times flushed the system and now its starting to make noise agian... why type of fluid is recomended?

 

apparently they use trans fluid...i used prestone multi-vehicle pwr steering fluid in mine...it's got a little bit of a groan when you're turning the wheel at idle...but it has since i got it...which, originally, was why i changed the fluid..it's got 103k on it..i changed the fluid about a thousand miles ago...its been doin fine other than the little groan..