while in park with engine running, slowly turn steering wheel left to right. If you hear a "squeaking" noise, more than likely you have a dry (meaning out of grease) pittman arm. The factory pittman arms dont have greasable zerks. But you can get a cheapo grease gun, a needle valve grease fitting, and squirt some grease into the pittman arm bushing (about $20 for the gun and fitting, or borrow one). My 97 f150 still has the factory pittman arm at 165,000 miles but i have to grease it once every 50,000 miles or so (an easy, 5 minute job). Or just get a new pittman arm installed that has greasable zerks. Cost is probably around $150 to $200 to change out the pittman arm at a shop.