More than likely the problem is inside the steering box. Our steering gears are known to have poor, loose fitting ball bearing in the recirculating ball sector shaft. Start your truck and with it idling have someone move the steering wheel back and forth until the wheels just start to move. Watch the rag joint going into the gear and the output shaft and steering arm. You will most likely see there is a fair of lost motion. Mine was that way and my rig only has 40,000 miles on it.
The cure is Red Head Steering Gears 206-364-3333 in Seattle. Harvey the owner has come up with oversized balls for them that really takes the slop out of the gear. He keeps about 15 of them rebuilt on the shelf all the time. The best money I have spent!
There is no comparison between one of his gears and one you would get from NAPA or Schucks.
Jim