2009 Chevrolet Avalanche Owner's Manual - Page 426

What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See Recommended Fluids and Lubricants on page 6-13. How to Check Lubricant Four-Wheel Drive Lubricant checks in this section also apply to these vehicles. There are two additional systems that need lubrication. Transfer Case When to Check Lubricant It is not necessary to regularly check transfer case fluid unless you suspect there is a leak, or you hear an unusual noise. A fluid loss could indicate a problem. Have it inspected and repaired. A. Fill Plug B. Drain Plug To get an accurate reading, the vehicle should be on a level surface. If the level is below the bottom of the fill plug hole, you will need to add some lubricant. Add enough lubricant to raise the level to the bottom of the fill plug hole. Use care not to overtighten the plug. Active Transfer Case 5-46