Chevrolet 1998 Tracker Owner's Manual page 260

How to Check Lubricant Front Axle
If the level is below the bottom of the filler plug hole,
you'll need to add some lubricant. Add enough lubricant
to raise the level to the bottom of the filler plug hole.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See "Recommended Fluids and
Lubricants" in the Index.
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant and when to change it. See
"Periodic Maintenance Inspections'' and "Scheduled
Maintenance Services" in the Index.
How to Check Lubricant
I
If the level is below the bottom of the filler plug hole,
you may need to add some lubricant.