GMC 2004 Canyon - Manual (Page 313)

Front Axle
When to Check and Change Lubricant
It is not necessary to regularly check front axle 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 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 6-13 to determine what kind of lubricant to use.
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