2011 Chevrolet Silverado 1500 Regular Cab Owner's Manual - Page 524

11-6 Service and Maintenance . First Engine Oil Change After Every 80 000 km/50,000 Miles . Engine air cleaner filter replacement. See Engine Air Cleaner/Filter on page 10‑20. Automatic transmission fluid change (severe service) for vehicles with Gross Vehicle Weight Rating (GVWR) over 3 901 kg (8,600 lbs) or mainly driven in heavy city traffic in hot weather, in hilly or mountainous terrain, when frequently towing a trailer, or used for taxi, police, or delivery service. See Automatic Transmission Fluid (4-Speed Transmission) on page 10‑13 or Automatic Transmission Fluid (6-Speed Transmission) on page 10‑16. . Four‐wheel drive only: Transfer case fluid change (severe service) for vehicles mainly driven when frequently towing a trailer, or used for taxi, police, or delivery service. Check vent hose at transfer case for kinks and proper installation. Check to be sure vent hose is unobstructed, clear, and free of debris. During any maintenance, if a power washer is used to clean mud and dirt from the underbody, care should be taken to not directly spray the transfer case output seals. High pressure water can overcome the seals and contaminate the transfer case fluid. Contaminated fluid will decrease the life of the transfer case and should be replaced. . Evaporative control system inspection. Check all fuel and vapor lines and hoses for proper hook‐up, routing, and condition. Check that the purge valve, if the vehicle has one, works properly. Replace as needed. An Emission Control Service. The U.S. Environmental Protection Agency or the California Air Resources Board has determined that the failure to perform this maintenance item will not nullify the emission warranty or limit recall liability prior to the completion of the vehicle's useful life. We, however, urge that all recommended maintenance services be performed at the indicated intervals and the maintenance be recorded.