1999 GMC C-SERIES automatic transmission

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2-21
CAUTION:
It is dangerous to get out of your vehicle if the
shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
Don't leave your vehicle when the engine is
running unless you have to. If you have left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure your
vehicle won't move, even when you're on fairly
level ground, always set your parking brake and
move the shift lever to PARK (P).
See ªShifting Into PARK (P)º in the Index.
CAUTION:
Shifting out of PARK (P) or NEUTRAL (N) while
your engine is ªracingº (running at high speed) is
dangerous. Unless your foot is firmly on the
brake pedal, your vehicle could move very
rapidly. You could lose control and hit people or
objects. Don't shift out of PARK (P) or
NEUTRAL (N) while your engine is racing.
Automatic Transmission Third Gear Hold
(If Equipped)
If you have this feature, your range selector has a
ª2
-3º position. You can't shift up to the next higher
gear when the transmission is in this position unless
your engine
-governed speed is exceeded, such as when
going downhill.
This feature is useful for certain load and traffic
conditions or when plowing snow. See the Allison
Automatic Transmission Operator's Manual in your
vehicle for further information.
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2-22
Manual Transmission Operation
This part of the manual covers the basics of the manual
transmission. With some of the transmissions, you
will find another manual in your vehicle that goes into
more detail.
Using the Clutch
When you're starting to move the vehicle, it's important
to begin with the engine speed at idle. Then start to
engage the clutch and listen for an engine speed drop of
about 100 rpm. At this point, the clutch is engaging, so
you should increase the engine speed and fully engage
the clutch. It's important not to increase the engine
speed sooner or before the clutch begins its engagement.
If you do, you can cause damage to your vehicle.
Double-Clutching
You must use the ªdouble-clutchingº method when you
shift an unsynchronized gear set. Simply disengage the
clutch, shift to NEUTRAL (N) and engage the clutch.
When you're shifting down to a lower gear, accelerate
the engine speed while in NEUTRAL (N) to get ready
for the lower gear.
Eaton Fuller 5 and 6-Speed Transmissions
and Dana Spicer 7-Speed Transmissions
These transmissions have gears that automatically
synchronize when you shift up or down (except
FIRST (1) gear on the five
-speed transmission which is
unsynchronized). Choose the gear which will maintain
the road speed you want while keeping the engine above
two
-thirds of the governed speed. When the engine
speed drops below two
-thirds of the governed speed,
shift into the next lower gear before your engine begins
to lug. When you shift down, be sure to double
-clutch
if required.
Eaton Fuller 9 and 10-Speed
Manual Transmissions
If your vehicle has one of these unsynchronized
transmissions, it's naturally somewhat complicated.
The label above the windshield will tell you the
operating basics you need to know.
Before operating the vehicle with one of these
transmissions, be sure to read the Eaton Fuller
Transmission Driver Instructions Manual in your vehicle.
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2-24 Hydraulic Brakes
If your vehicle has hydraulic brakes, it has a parking
brake lever or an electric/hydraulic parking brake. The
lever is below the instrument panel to the left of the
steering column. The electric/hydraulic parking brake
knob is to the right of the steering column.
Your vehicle may also be equipped with an automatic
transmission which has a shift lever. This lever will have
a PARK (P) position on the shift indicator. When the
PARK (P) position is selected with the shift lever, the
parking brake is automatically applied.
Propshaft Brake Burnish Procedure
It is recommended that the propshaft-mounted parking
brake be burnished as part of the new vehicle break
-in.
The parking brake will work best after it has been
burnished following these instructions.
Make 10 stops, using the parking brake hand lever, from
20 mph (32 km/h) about 2 1/2 miles (4 km) apart.
Between stops, drive the vehicle at 20 mph (32 km/h).
Lever Operated Parking Brake
To apply the parking brake,
pull the lever all the way up.
The PARK BRAKE light
will come on when the
parking brake is applied.
Then shift the transmission
to NEUTRAL (N) or
PARK (P).
The vehicle must be stopped when applying the parking
brake, except while burnishing the parking brake linings
(see ªPropshaft Brake Burnish Procedureº in the Index).
You can easily adjust the parking brake by turning the
knob on the lever. Turning it clockwise makes the brake
grip more tightly. It will also make the lever seem harder
to pull up. Turning the knob counterclockwise makes the
parking brake apply less firmly. Adjust the parking
brake only when the lever is down (released).
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2-25
If your parking brake doesn't hold the vehicle when
applied, see your GM Truck dealer who can adjust your
parking brake properly.
To release the parking
brake, first push down the
regular brake pedal. Then,
push the parking brake lever
all the way down and shift
the automatic transmission
to NEUTRAL (N).
The PARK BRAKE light will remain illuminated if the
parking brake is not fully released.
NOTICE:
Driving with the parking brake on can overheat
the parts in the system. You may have to replace
them, and you could also damage other parts of
your vehicle.
Electric/Hydraulic Parking Brake
(If Equipped)
CAUTION:
It will take a few seconds for the parking brake
to fully apply, and even longer when it is cold
outside. Do not leave your vehicle until the
parking brake applies fully. Without the parking
brake applied, your vehicle is free to move. It
could hit someone or something.
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2-26
If your vehicle has this
system, you will have a
knob to the right of the
steering column.
To apply the parking brake, pull the knob toward you.
Then shift the transmission to NEUTRAL (N) or
PARK (P).
Push the knob in to release the parking brake. The
ignition must be in RUN and the shift lever out of
PARK (P) in order to release the parking brake.
The parking brake will automatically apply if the
ignition is turned off and in PARK (P) and will also
apply (will not release) if the vehicle's battery is dead
or disconnected.The PARK BRAKE light may flash while the parking
brake is being applied or released. This is normal for
this system.
If your vehicle needs towing or the parking brake will
not release, the towing operator will need to disconnect
the propshaft before towing your vehicle. See ªTowing
Your Vehicleº in the Index.
Air Brake (If Equipped)
CAUTION:
When the yellow SYSTEM PARK and the red
TRAILER AIR SUPPLY knobs are both pushed
in, your rig will be free to move. It could strike
someone or something. When both of these knobs
are pushed in, either hold the regular brake
pedal down or, if you have it, pull out the blue
TRACTOR PARKING knob, to keep your rig
from moving.
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2-28
CAUTION:
If you apply any one of the air brake parking
controls while the vehicle is moving, your rig will
stop suddenly. If you are not ready for this, you
or others could be injured. Don't apply any one
of these controls while you're driving, unless you
have to make an emergency stop.
If the air pressure drops below 60 to 70 psi (413 to
482 kPa), the PRIMARY BRAKE light will come on. If
the air pressure drops to 40 to 45 psi (275 to 309 kPa), the
yellow knob will automatically pop out and apply the
spring brakes. If you ever have a complete loss of air so
that your air brakes automatically apply, there is a way that
the tow operator can release the parking brakes to tow the
vehicle. See ªTowing Your Vehicleº in the Index.
CAUTION:
If your vehicle is left in gear, the engine can
start if the vehicle starts to roll. This can easily
happen if you have the diesel engine. Shift the
transmission into NEUTRAL (N) before you
leave the vehicle.
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2-30
Running Your Engine While You're
Parked (Automatic Transmission)
It's better not to park with the engine running. But if
ever you have to, here are some things to know.
CAUTION:
Idling the engine with the climate control system
off could allow dangerous exhaust into
your vehicle (see the earlier Caution under
ªEngine Exhaustº).
Also, idling in a closed-in place can let deadly
carbon monoxide (CO) into your vehicle even if
the fan switch is at the highest setting. One place
this can happen is a garage. Exhaust
-- with
CO
-- can come in easily. NEVER park in a
garage with the engine running.
Another closed-in place can be a blizzard.
(See ªBlizzardº in the Index.)
CAUTION:
It can be dangerous to get out of your vehicle
without the parking brake firmly set. Your
vehicle can roll. If you've left the engine running,
the vehicle can move suddenly. You or others
could be injured. To be sure your vehicle won't
move, even when you're on fairly level ground,
always set your parking brake.
Follow the proper steps to be sure your vehicle
won't move.
Windows
Manual Windows
Turn the hand crank on each door to raise or lower
the window.
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2-36 Cruise Control (If Equipped)
With cruise control, you can
maintain a speed of about
30 mph (48 km/h) or more
without keeping your foot
on the accelerator. Cruise
control does not work at
speeds below about 30 mph
(48 km/h).
If you have an automatic transmission and you apply
your brakes, the cruise control will shut off.
If you have a manual transmission and you apply your
brakes or push the clutch pedal, the cruise control will
shut off.CAUTION:

Cruise control can be dangerous where you
can't drive safely at a steady speed. So,
don't use your cruise control on winding
roads or in heavy traffic.

Cruise control can be dangerous on
slippery roads. On such roads, fast changes
in tire traction can cause needless wheel
spinning, and you could lose control. Don't
use cruise control on slippery roads.
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