2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 518

When to Change Lubricant Refer to the Maintenance Schedule to determine how often to change the lubricant. See Scheduled Maintenance on page 7‑3. How to Check Lubricant To get an accurate reading, the vehicle should be on a level surface. What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See Recommended Fluids and Lubricants on page 7‑13. 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. 1500 Series A: Fill Plug B: Drain Plug 6-58