Chevrolet Tahoe Owner's Manual page 373

It is not necessary to regularly
check front axle fluid unless a leak
is suspected, or an unusual noise is
heard. A fluid loss could indicate a
problem. Have it inspected and
repaired.
To get an accurate reading, the
vehicle should be on a level
surface.
A. Fill Plug
B. Drain Plug
When the differential is cold, add
enough lubricant to raise the
level from 0 mm (0 in) to 3.2 mm
(1/8 in) below the fill
plug (A) hole.
When the differential is at
operating temperature (warm),
add enough lubricant to raise the
level to the bottom of the fill
plug (A) hole.
Refer to
determine what kind of lubricant
to use.
It is not necessary to regularly
check rear axle fluid unless there is
a leak suspected, or an unusual
noise is heard. A fluid loss could
indicate a problem. Have it
inspected and repaired.
All axle assemblies are filled by
volume of fluid during production.
They are not filled to reach a certain
level. When checking the fluid level
on any axle, variations in the
readings can be caused by factory
fill differences between the minimum
and the maximum fluid volume.
to