1997 Chevrolet Blazer Owner's Manual - Page 277

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 "Scheduled Maintenance Services" in the Index. If the level is below the bottom of the filler plug hole, you'll need to add some lubricant. If the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole. If the differential is cold, add enough lubricant to raise the level to 1/2 inch (: 12 mm) below the filler plug hole. How to Check Lubricant What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See "Recommended Fluids and Lubricants" in the Index. 6-22