2009 GMC Canyon Owner's Manual - Page 294

How to Check Lubricant If the level is below the bottom of the filler plug hole, located on the front axle, you may need to add some lubricant. When the differential is cold, add enough lubricant to raise the level to 1/2 inch (12 mm) below the filler plug hole. When the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole. What to Use See Recommended Fluids and Lubricants on page 6-11 to determine what kind of lubricant to use. To get an accurate reading, the vehicle should be on a level surface. 5-46