2003 GMC Sierra 1500 Pickup Owner's Manual - Page 432

Rear Axle When to Check Lubricant Refer to the Maintenance Schedule to determine how often to check the lubricant. See Part A: Scheduled Maintenance Services on page 6-4. To get an accurate reading, the vehicle should be on a level surface. The proper level for the 1500 Seriesis from 5/8 inch to 1 5/8 inch(15 mmto 40 mm) belowthe bottom of the filler plug hole. The proper level for the 1500 HD Series, 2500 Series, 2500 HD, and 3500 Series is from 0 to 112 inch (0 to 13mm) below the bottom of filler plug the hole. The proper level for the 1500 and 2500 Series vehicles with QUADRASTEERTM Wheel Steer) is from (4 0 to 1/4 inch (0 to 6 mm) below thefiller plug hole. Add only enoughfluid to reach the properlevel. How to Check Lubricant What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See Part D: Recommended Fluids and Lubricants on page 6-18. I 1500 Series Shown, 2500 Series Similar 5-57