Hummer 2006 H2 - Manual (Page 374)

How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
When the differential is cold, the proper level is from
5/8 inch to 1-5/8 inch (15 mm to 40 mm) below the
bottom of the filler plug hole, located on the rear axle.
Add only enough fluid to reach the proper level.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See Recommended Fluids
and Lubricants on page 6-12.
Four-Wheel Drive
Transfer Case
It is not necessary to regularly check transfer case 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.
Refer to the Maintenance Schedule to determine how
often to change the lubricant. See Scheduled
Maintenance on page 6-4.
5-44