I noticed many complaints about brake noise and I believe that many of them may be the same as my problem.

Since new the truck made a high pitch noise at low speed, It was hard to tell where it comes from, but after 20,000 miles I've found it. My dealer was only interested in billing GM for warranty work. I ruled out brakes as it does it if you ride them, and sometimes you can hear it when not moving. Early on they looked for vac leaks, then the alternator, then the power steering pump. It wasn't until I discovered that if you tweak the steering wheel a bit left or right when driving you can make the noise go away. Also when not moving, the noise will not occur if the wheels are turned all the way left or right. Recently I learned that this does not make the noise when the air temp is near zero. I am going to put a different power steering fluid in the system that has a viscosity near that of GM's standard fluid when at 0 degrees. http://www.championbrands.com/SpecSheet/4182spec.pdf see link for data on GM's oil. There are technical bulletins pertaining to this issue but are as yet unresolved.