2004 GMC Sonoma Owner's Manual - Page 291

How to Check Lubricant Front Axle When to Check and Change Lubricant Refer to the Maintenance Schedule to determine how often to check the lubricant and when to change it. See Part A: Scheduled Maintenance Services on page 6-4. How to Check Lubricant To get and accurate reading, the vehicle should be on a level service. If the level is below the bottom of the filler plug hole, you'll need to add some lubricant. Remove the plug and add enough lubricant to raise the level to the bottom of the filler plug hole. Use care not to overtighten the plug. 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 6-32. To get an accurate reading, the vehicle should be on a level surface. 5-47