GMC C-Series 2001 Owner's Manual page 66

Air Shift Control
(Manual Transmissions Only)
When the lever is moved to HI, the rear axle will be in
the high range. Switch it to LOW to get the low range.
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The two speed axle should be in LOW when you park
the vehicle.
You'll need to engage the transmission, even moving the
vehicle a little, to be sure the axle is in the low range.
Then apply the parking brake, shift into NEUTRAL and
shut off the engine.
2-22
The lever for the rear axle
shift control is either at the
lower right corner of the
instrument panel or on the
shift lever.
Also, always start the vehicle in motion with the
-
two speed axle in the LOW position. When you upshift
the rear axle from LOW to HI, move the lever to the HI
position, disengage the clutch, pause, engage the clutch
and then press down on the accelerator. When you shift
the axle down from HI to LOW, you don't have to
clutch. Just move the lever to LOW, release the
accelerator and then quickly press it down again.
Air Suspension (If Equipped)
Your vehicle may be equipped with the Hendrickson
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HAS Series single axle air suspension which is designed
- -
for single axle on highway use. This feature is available
in 19,000 lb. and 23,000 lb. capacities and as a low
profile option for operations which require extra cubic
capacity and a reduced deck height.
With this air suspension system, the ride height is set
during vehicle assembly so that the vehicle has a
constant frame height. The system will then increase
or decrease air pressure in the air springs to maintain
this height.