1997 GMC Sonoma Owner's Manual - Page 261

What to Use Refer to the Maintenance Schedule to determine what kind of lubricant touse. See "Recommended Fluids and Lubricants" in the Index. How to Check Lubricant Four-wheel Drive Most lubricant checks in this section also apply to four-wheel-drive vehicles. However, they have two additional systemsthat need lubrication. Transfer Case When to Check Lubricant Refer to the Maintenance Schedule to determinehow often to check the lubricant. See "Periodic Maintenance Inspections" in the Index. 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. What to Use Refer to the Maintenance Schedule to determinewhat kind of lubricant to use. See "Recommended Fluids and Lubricants" in the Index. 6-23