Chevrolet EXPRESS - 2011 Manual page 304

Refer to the Maintenance Schedule
to determine how often to check the
lubricant and when to change it.
See
.
To get an accurate reading, the
vehicle should be on a level
surface.
If the level is below the bottom of
the fill plug hole, some lubricant
may need to be added.
When the differential is cold,
add enough lubricant to raise the
level to 10 mm (3/8 in) below the
fill plug hole.
When the differential is at operating
temperature (warm), add enough
lubricant to raise the level to the
bottom of the fill plug hole.
Refer to
determine what kind of
lubricant to use.
to