1999 GMC C-SERIES suspension

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1-12 Lap-Shoulder Belt
The driver has a lap-shoulder belt. Here's how to wear
it properly.
1. Close and lock the door.
2. Adjust the seat (to see how, see ªSeatsº in the Index)
so you can sit up straight.
Bench (A)
Suspension (B)
3. Pick up the latch plate and pull the belt across you.
Don't let it get twisted.
4. Push the latch plate into the buckle until it clicks.
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1-13
For suspension-type seats (B), if the belt stops before
it reaches the buckle, tilt the latch plate and keep
pulling until you can buckle the belt. Pull up on the
latch plate to make sure it is secure. If the belt is
pulled out all the way so that it locks, press down on
the button on the retractor cover to make it retract.
If the belt isn't long enough, see ªSafety Belt
Extenderº at the end of this section.
Make sure the release button on the buckle is
positioned so you would be able to unbuckle the
safety belt quickly if you ever had to.
Suspension (B)
5. To make the lap part tight on suspension
-type
seats (B), pull down on the buckle end of the belt as
you pull up on the shoulder belt.
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1-20
Bench (A)Suspension (B)
To unlatch the belt, just push the button on the buckle.
The belt should go back out of the way. For a
suspension
-type seat, if the belt is pulled out all the way
so that it locks, press down on the button on the retractor
cover to make it retract.
Before you close the door, be sure the belt is out of the
way. If you slam the door on it, you can damage both the
belt and your vehicle.
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2-19 Air Shift Control
(Manual Transmissions Only)
The lever for the rear axle
shift control is either at the
lower right corner of the
instrument panel or on the
shift lever.
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.
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.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
HAS Series single
-axle air suspension which is designed
for single
-axle on-highway use. This feature is available
in the 19,000 lb. capacity 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.
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2-20
Air Suspension Dump Control (If Equipped)
If your vehicle is equipped with the Hendrickson HAS
Series single
-axle air suspension, you may have this
control. The air suspension dump control allows the
operator to lower the deck height approximately
4.5 inches (11.5 cm) from the normal frame height.
The switch to deflate and
inflate the air suspension is
located on the upper left
side of the instrument panel
above the driver's side vent.
The light in the switch will be illuminated whenever the
switch is in the ªdumpedº position.
Automatic Transmission Operation
We build vehicles with four, five and six-speed
automatic transmissions. This part of the manual covers
the basics of these. With some of the transmissions, you
will find another manual in your vehicle that goes into
more detail. On the ceiling, in front of and above the
driver, or in some other place near the driver, you will
see a label that describes important operating facts about
the automatic transmission in your vehicle. Make sure
you follow the instructions on this label.
You may have a PARK (P) position for your shift lever.
This position locks your rear wheels. It is the best
position to use when you start your engine because your
vehicle can't move easily.
All vehicles equipped with automatic transmissions
can be started in PARK (P), if equipped, or in
NEUTRAL (N). When you shift out of NEUTRAL (N),
you may have to hold in a push button on the shift lever
or lift up on a release handle as you shift. See the
Allison Automatic Transmission Operator's Manual in
your vehicle for more information about this.
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4-30
Using heavier suspension components to get added
durability might not change your weight ratings. Ask
your dealer to help you load your vehicle the right way.
NOTICE:
Your warranty does not cover parts or
components that fail because of overloading.
If you put things inside your vehicle -- like suitcases,
tools, packages or anything else
-- they will go as fast as
the vehicle goes. If you have to stop or turn quickly, or
if there is a crash, they'll keep going.
CAUTION:
Things you put inside your vehicle can strike and
injure people in a sudden stop or turn, or in
a crash.

Put things in the cargo area of your vehicle.
Try to spread the weight evenly.

Never stack heavier things, like suitcases,
inside the vehicle so that some of them are
above the tops of the seats.

Don't leave an unsecured child restraint in
your vehicle.

When you carry something inside the
vehicle, secure it whenever you can.
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5-13
A. Hardwood Board
B. Swing Arm
5. Raise the vehicle to the required height.Single Drive Rear Axle
Disconnect the propshaft at the rear axle. Secure the
propshaft to the frame or crossmember.
Tandem Drive Rear Axles
-- Forward Axle Off
the Ground
Raise the front of the vehicle until the forward
tandem axle wheels are off the ground. Remove the
rearward propshaft.
Tandem Drive Rear Axle
-- Both Axles on the
Ground Due to Type of Suspension or Attached Load
Disconnect the propshaft at the forward tandem axle.
Secure the propshaft to the frame or crossmember.
If there is damage or suspected damage to the axle(s),
remove all axle shafts. Cover the hub openings to
prevent the loss of lubricant or entry of dirt or
foreign objects.
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6-71
Name Circuits Protected
CHAS Exhaust Brake, Air Suspension
Dump Valve, Air Dryer, HYD
ABS ECHU
PARK LP Auxiliary Wiring, Air Conditioner
Controls, Parking Lamps, Turn
Signals, Taillamps, Stoplamps,
Marker Lamps, Trailer Running
Lamps, Lighted Mirrors, Radio
Receiver, Mirror Clearance Lamps
HORN Horn/Diagnostic Connector
PRK BRK Parking Brake Module
FUEL Heated Fuel Filter (Diesel
Engines) or Fuel Pump
(Gasoline Engines)
AXLE Heated Mirrors, Radiator Shutters,
Tw o
-Speed Axle Motor,
Tw o
-Speed Axle Switch
MRKR LP Roof Marker Lamps,
Trailer Marker Lamps,
Marker Lamp RelayName Circuits Protected
CIG/AUX Cigarette Lighter,
Auxiliary Power Jacks
AUX Auxiliary Wiring Relay
IGN RLY/VIN Vehicle Interface Module
(Diesel Engines) or Generator,
Coil, Injectors (Gasoline Engines)
WDO Power Windows
CRNK Starter Relay
IGN SW Instrument Panel Cluster Telltales
AUX Auxiliary Wiring
RDO Radio, Auxiliary Wiring
DR LK Power Door Locks
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