GMC 2008 Envoy - Manual (Page 341)

How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
The proper level is from 0 to 0.40 inch (0 to 10 mm)
below the bottom of the filler plug hole, located on the
rear axle.
What to Use
To determine what kind of lubricant to use, see
Recommended Fluids and Lubricants on page 6-12.
Four-Wheel Drive
Transfer Case
When to Check Lubricant
It is not necessary to regularly check fluid unless you
suspect there is a leak or you hear an unusual noise.
A fluid loss could indicate a problem. Have it inspected
and repaired.
How to Check Lubricant
To get an accurate
reading, the vehicle should
be on a level surface.
If the level is below the bottom of the filler plug hole,
you will 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 the plug.
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