99 suburban noise

I have a noise coming from my suburban. The noise starts at about 20mph. The faster I go the louder it gets. If I put on the cruise or stay on the throttle the noise is there, but as soon as I turn off cruise or let off the gas pedal the noise goes away after a couple of seconds. I replaced the u-joints on both shafts. I checked the fluids. I have no movement on the front shaft up or down. The back shaft moves up and down a little. Could the bearings in transfer case be bad?


Which end of the vehicle is the noise coming from?

sounds like it is coming from the middle underneath.