All of a suden I have a noise at about 20mph and up. It almost sounds as maybe the air compressor for the suspensioin may be running or something like that. Even my wife noticed it and she doesn't notice anything. It will go back to the dealer on Monday. Any ideas? Also lately the mileage has dropped off and the low traction light is coming on a lot.

Could be a wheel speed sensor. The buzzing could be the anti-loc system.
Check for ice build-up inside the wheels.
GM tech can scan it to tell for sure.

Yes, the dealer can scan it to tell you what the problem is, but they will charge you like $85 just for the scan!

Shawn

This sounds similar to the noise that I had coming from a bad front wheel hub. I had the buzzing/ grinding noise, and problems with the Traction Control and ABS lights.

Could be brittle brake pads that are chipping and scratching you're rotars as you drive.

Aubrun wins the cigar and my admiration. it was the left front wheel hub. Never had one of those go bad before.

Yes, because the WSS is integral to the hub, when it starts to go it can play havoc with the TC and ABS systems.