1998 Chevrolet Blazer Owner's Manual - Page 291

Rear Axle When to Check and Change Lubricant Refer to theMaintenance Schedule to determine how often to check the lubricant and when to change it. See "Scheduled Maintenance Services" in the Index. How to Check Lubricant If the level is below bottom of the filler plug hole, the you'll need to add some lubricant. Add enough lubricant to raise the level to the bottom of the filler plug hole. What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See "Recommended Fluids and Lubricants" in the Index. 6-21