2009 GMC Sierra 1500 Crew Cab Owner's Manual - Page 463

• For all 6.0L and 6.2L 2500HD Series applications, the proper level is from 0 to 0.5 inches (0 mm to 13 mm) below the bottom of the filler plug hole, located on the rear axle. Add only enough fluid to reach the proper level. Four-Wheel Drive Lubricant checks in this section also apply to these vehicles. • For all 6.6L DURAMAX DIESEL 2500HD Series applications and all 3500 Series applications, the proper level is from 0.6 inches to 0.8 inches (17 mm to 21 mm) below the bottom of the filler plug hole, located on the rear axle. Add only enough fluid to reach the proper level. 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. What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See Recommended Fluids and Lubricants on page 6-15. 5-53