Four Wheel Drive; Transfer Case - GMC 2002 Yukon XL Owner's Manual

How to Check Lubricant
1500 Series shown, 2500 and 3500 Series similar
To get an accurate reading, the vehicle should be on a
level surface.
The proper level for the 1500 Series is from 5/8 inch to
1 5/8 inch (15 mm to 40 mm) below the bottom of the
filler plug hole. The proper level for the 2500 Series is
from 0 to 3/8 inch (0 to 10 mm) below the bottom of the
filler plug hole. Add only enough fluid to reach the
proper level.
6-28
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See "Recommended Fluids and
Lubricants" in the Index.
Four Wheel Drive
-
Lubricant checks in this section also apply to these
vehicles. However, there are two additional systems that
need lubrication.

Transfer Case

When to Check Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant. See "Periodic Maintenance
Inspections" in the Index.