1994 Chevy Silverado rotating noise

Question, I have a 1994 chevy z-71 silverado truck with 181,000 miles that seems to be making a rotating noise. It is more noticeable on low drive speeds. The faster I speed up, m the noise follows.I can actually hear the full revolution of what seems a tire. The noise is not heard on any turns. Straight driving only. I have replaced the tires, replaced the passenger side wheel hub, thinking this was it. The noise seems to be under the floor board. I cannot really tell front or back. Please advise.