2009 GMC Yukon Owner's Manual - Page 447

• For all 6.0L 1500 series and all 6.2L non-all wheel drive 1500 series luxury model applications, the proper level is from 0.6 inch to 1.6 inches (15 mm to 40 mm) below the bottom of the filler plug hole, located on the rear axle. Add only enough fluid to reach the proper level. How to Check Lubricant • The proper fill level for the 2500 series is from 0 to 1/2 inch (0 to 13 mm) below the bottom of the filler plug hole, located at the front of the axle. Add only enough fluid to reach the proper level. Four-Wheel Drive Lubricant checks in this section also apply to these vehicles. There are two additional systems that need lubrication. Active Transfer Case 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. 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. 5-51