2008 Chevrolet Silverado 1500 Pickup Owner's Manual - Page 552

(l) Extreme Duty Service: Change transfer case fluid if the vehicle is mainly driven off-road in four-wheel drive, or is used for heavy trailer towing. Farming, mining, forestry, and Department of Natural Resources (DNR) vehicles meet this definition. (m) Severe Service: Change transfer case fluid if the vehicle is mainly used for trailer towing or driven in city traffic, wet environment, or high ambient temperatures. (n) Vehicles with diesel engine or with GVWR above 10,000 lbs (4 536 kg) only: Inspect shields for damage or looseness. Adjust or replace as required. This is a Noise Emission Control Service. Applicable to vehicles sold in the United States and recommended for vehicles sold in Canada. (p) If you drive regularly under dusty conditions, inspect the filter or change indicator (if equipped) at each engine oil change. (q) Visually inspect belt for fraying, excessive cracks, or obvious damage. Replace belt if necessary. Owner Checks and Services These owner checks and services should be performed at the intervals specified to help ensure the safety, dependability, and emission control performance of your vehicle. Your dealer/retailer can assist you with these checks and services. Be sure any necessary repairs are completed at once. Whenever any fluids or lubricants are added to your vehicle, make sure they are the proper ones, as shown in Recommended Fluids and Lubricants on page 6-14. At the First 100, 1,000 and 6,000 Miles (160, 1 600 and 10 000 km) For vehicles with dual wheels, check dual wheel nut torque. For proper torque, see Capacities and Specifications on page 5-133. At Each Fuel Fill It is important to perform these underhood checks at each fuel fill. 6-10