GMC 2006 Sierra - Manual (Page 470)

Rear Axle
When to Check Lubricant
It is not necessary to regularly check rear axle fluid
unless you suspect there is a leak or you hear an
unusual noise. 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.
Also, if a vehicle has just been driven before checking the
fluid level, it may appear lower than normal because fluid
has traveled out along the axle tubes and has not drained
back to the sump area. Therefore, a reading taken five
minutes after the vehicle has been driven will appear to
have a lower fluid level than a vehicle that has been
stationary for an hour or two. Remember that the rear
axle assembly must be supported to get a true reading.
How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
• The proper level for the 1500 Series is from
5/8 inch to 1 5/8 inch (15 mm to 40 mm) below
the bottom of the filler plug hole.
• The proper level for the 1500HD Series,
2500 Series and 2500HD Series with the
6.0L V8 engine (RPO LQ4) is from 0 to 1/2 inch
(0 to 13 mm) below the bottom of the filler plug hole.
1500 Series Shown, 2500 Series Similar
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