2009 GMC Sierra 1500 Crew Cab Owner's Manual - Page 466

Front Axle When to Check and Change Lubricant It is not necessary to regularly check front axle 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. How to Check Lubricant To get an accurate reading, the vehicle should be on a level surface. All except 1500 Series A: Fill Plug B: Drain Plug • When the differential is cold, add enough lubricant to raise the level from 0 (0 mm) to 1/8 inch (3.2 mm) below the filler plug hole. • When the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole. 1500 Series A: Fill Plug B: Drain Plug 5-56 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.