It's a ford. They all make noise after awhile. You could replace the pump if you want but if you can put with the noise, that pump will last a long time. Prolly for as long as you have the truck. I once got stuck in my old 2wd ranger and during the process my p/s pump got so hot that the fluid actually came out of the top of the res. and was all over the engine. The pump was actually knocking. lol. I filled it back up and drove it for another 150,000 miles with the pump making a whining noise. Then I sold the truck.
2003 Ranger FX4 level II. 3" BL, 33x12.50 GT Radial Mud Claws, Custom front and rear bumpers with winch hookups, custom flatbed, with hi-lift, and full size spare mount, 12,000 lb winch mounted under bed, Electric fan, and of course a flowmaster.