rear end noise

Its probably the ring and pinion wearing out, and if the sound changes when you get on the gas and let off I would say its the ring and pinion gear going bad, As it wears it will get louder.

Mine literally ran out of fluid about 3-4 yrs ago in 2008. Put in 2 quarts rear end fluid and took it in for service on the extended warranty. $1150 for the repair. No deductible. Have since filled it about 1/2 quart at time, every yr since. no apparent leaks. I have no idea where it is going. when you get it fixed be sure to check the rear diff fluid often. So after four yrs of not checking from buying the BURB new, the rear end failed. The chevy book that comes with the car says to wait until you hear a noise before doing anything. YA RIGHT. Have it checked when the oil is changed(only takes a minute) and add only synthetic.