Oldsmobile 2001 Silhouette Owner's Manual page 365

All Wheel Drive (Option)
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If you have an all wheel drive vehicle, be sure to perform
the lubricant checks described in this section. However,
they have two additional systems that need lubrication.
Transfer Case (Power Transfer Unit)
When to Check Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant. See "Periodic Maintenance
Inspections" in the Index.
How to Check Lubricant
6-24
To get an accurate reading, the vehicle should be on a
level surface.
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.