I started hearing this noise under my 2003 Z71 Silverado a couple of weeks ago and it has gotten progressively worse. It's hard to descibe. At slow speed 1-2 MPH it sounds like a rubber/gasket rubbing against something in the middle of the truck underneath. As I go faster it increases in pitch, until I get to about 30MPH then I can't hear it anymore. Anyone out there with some 2 cents to put in?? Thanks

I would have a close look at the drive shaft and center carrier bearing and rubber mount.
MT