GMC Yukon Denalid Owner's Manual page 472

How to Check Lubricant
To get an accurate reading, the vehicle should be
on a level surface.
A: Fill Plug
B: Drain Plug
472
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 from 0 (0 mm)
to 1/8 inch (3.2 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
Refer to the Maintenance Schedule to determine
what kind of lubricant to use. See Recommended
Fluids and Lubricants on page 561.