Have a 05 F150 5.4L 4x4, been having very loud power steering whine. Louder with speed and load not rpms, at idle no noise at all and can rev with no noise, noise starts in between 15-20mph. Low speeds{15-30mph} will quiet when turning left and louder when right. Have replaced pump, checked for restrictions in cooler and pressure lines. Also gets really bad when suspension flexes or wheels are jacked up, almost a growling and can feel it steering wheel, then the growling gradually goes away after driving but goes back to the wine. Im leaning towards the steering rack but just want to know if anyone has ever ran across this or have any suggestions.