Chevrolet 2005 Silverado 1500 Pickup Owner's Manual page 451

How to Check Lubricant
All-Wheel Drive Transfer Case
A. Fill Plug
B. Drain Plug
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,
located on the all-wheel drive transfer case, you'll 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.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See Recommended Fluids
and Lubricants on page 6-13.
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