GMC 1996 Sierra Owner's Manual page 274

Rear Axle
When to Chc d Change Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant and when to change it. See
"Scheduled Maintenance Services" in the Index.
How to Check Lubricant
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.
C3 (3500 HD) Trucks Equipped with
Dana Rear Axle
Additional rear axle scheduled maintenance is required
on
3500 HD models equipped with Dana rear axles
when they are driven under the following conditions:
Extreme loading (at or near GVWR) or trailer
towing, and:
0
Operation above 45 mph (70 km/h) for extended
periods of time
Vehicles used in any of these conditions require the
rear axle lubricant be changed every 30,000 miles
(SO
000 km). Fluid capacity
is
4.12 quarts (3.9 L).
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant
to
use. See "Recommended Fluids and
Lubricants" in the Index.
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