I have a 2000 Sierra with 89,000 miles. At very low speed, 5 MPH, I have a very difficult time turning the wheel to the right. It is almost like there is no power steering. Any ideas what would cause this?

Bill

 

power steering pump.

 

There is a TSb, although I cant seem to find it, that adresses the issue in the power steering gear box valves sticking, my '99 had the same issue. I beleive the fix was to flush the fluid and add 15-20% Marvel Mystery oil or a Lucas product when refilling. This is supposed to free up the valves.
Check with GM for the correct additive