Power steering problems -'99 Sierra 1500

I need help solving this problem. The truck has power steering when its turning to the left, but no power steering when its turning to the right. I've checked the fluid level, and there are no leaks that I can find.
Has anyone ever had this issue?

Assist in only one direction usually indicates a problem with the steering gear box valving. The power steering pump does not care what direction you are turning. Lift the front end and turn the steering linkage side to side to be sure it moves freely both ways (engine off). The problem is most likely in the steering gear.