Sorry, the NHTSA has not posted this TSB document yet.
You can still get the detailed info from Chevrolet for this TSB. Call your local Chevrolet dealer's service department & ask for a copy of TSB# TB-11-03-08-001.
GM: 2006-2011 IMPALA. THERE IS A GROWL NOISE IN THE FRONT OF THE VEHICLE WHEN DRIVING 20-50MPH. THIS MAY BE CAUSED BY A LOSS OF PRELOAD ON THE WHEEL BEARINGS. *RM