1994 GMC Suburban Owner's Manual - Page 281

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. How to Check Lubricant 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 toraise the level to 1/2 inch ( 1 2 mm) below 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. Engine Coolant The following explainsyour cooling system and how to add coolant when it is low. If you have a problem with engine overheating,see "Engine Overheating'' in the Index. The proper coolant foryour vehicle will: 0 Give freezing protection down to -20" F (-29"C), or -34°F (-37 "C) in Canada and for vehicles with the cold climate option. Give boiling protection up to25 8O F ( 125" C ) . Protect against rust and corrosion. Help keep the proper engine temperature. Let the warning lights and gages work as they should. 0 0 0 6-35