2000 Chevrolet Suburban Owner's Manual - Page 320

The proper level for the 1500 Series is from 5/8 inch to 1 5/8 inch (15 mm to 40 mm) below the filler plug. The proper level for the 2500 Series is from 0 to 3/8 inch (0 to 10 mm) below the filler plug. Add only enough fluid to reach the proper level. 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. Four-Wheel Drive Most lubricant checks in this section also apply to four-wheel-drive vehicles. However, they have two additional systems that need lubrication. Automatic Transfer Case If the level is below the bottom of the filler plug hole, you'll need to add some lubricant. Add enough lubricant to raise the level to the bottom of the filler plug hole. Use care not to overtighten plug. What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See "Recommended Fluids and Lubricants" in the Index. Transfer Case When to Check Lubricant Refer to the Maintenance Schedule to determine how often to check the lubricant. See "Periodic Maintenance Inspections" in the Index. 6-21