Your truck has Rack and Pinion steering. Usually they last many years, but it sounds like you may have the output bushings going bad. When they go bad, it requires more effort to turn the wheel. Also, make sure all greaseable steering components are properly greased and none are bad. Also, make sure the belt is tight enough so the pump isn't slipping.
Let me know if you have other questions.
Wednesday, January 13th, 2010 AT 10:30 PM