The Driver-side on my Truck when out at 70,000 miles and I replaced both Driver & Passenger side at the same time and when with.....Timken's, hopefully your Dealer will take care of this for you and replace them under your Warranty,
Link,
http://cgi.ebay.com/ebaymotors/Hub-Bearing-Assembly-Chevrolet-Silverado-1500-Timken-/290543996008?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AChevrolet|Model%3AAvalanche+1500&hash=item43a5c58c68
Link,
http://cgi.ebay.com/ebaymotors/Hub-Bearing-Assembly-Chevrolet-Silverado-1500-Timken-/290543996008?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AChevrolet|Model%3AAvalanche+1500&hash=item43a5c58c68