1999 GMC SIERRA clutch

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2-13 Key Release Button (Manual Transmission)
The ignition key cannot be
removed from the ignition
of manual transmission
vehicles unless the key
release button is used.
To remove the key on manual transmission vehicles,
turn the key to OFF, then press the button and turn the
key to LOCK. Do not hold the button in while turning
the key to OFF. Keeping your finger on the button, pull
the key straight out.
On automatic transmission vehicles, turn the key to
LOCK and pull it straight out.
Starting Your Gasoline Engine
If you have a diesel engine, see ªStarting Your Diesel
Engineº in the Diesel Engine Supplement.
Automatic Transmission
Move your shift lever to PARK (P) or NEUTRAL (N).
Your engine won't start in any other position
-- that's a
safety feature. To restart when you're already moving,
use NEUTRAL (N) only.
NOTICE:
Don't try to shift to PARK (P) if your vehicle is
moving. If you do, you could damage the
transmission. Shift to PARK (P) only when
your vehicle is stopped.
Manual Transmission
The gear selector should be in NEUTRAL and the
parking brake engaged. Hold the clutch pedal to the floor
and start the engine. Your vehicle won't start if the clutch
pedal is not all the way down
-- that's a safety feature.

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2-19
Manual Transmission Operation
5-Speed (If Equipped)
Here's how to operate
your transmission.
FIRST (1) is intended only for heavy loads and is not
recommended for normal driving.
During the first 500 miles (805 km) of vehicle use, start
your vehicle moving in FIRST (1). This allows clutch
components to break
-in properly.
FIRST (1): Press the clutch pedal and shift into
FIRST (1). Then, slowly let up on the clutch pedal as
you press the accelerator pedal. Shift into FIRST (1)
only when the vehicle is below 5 mph (8 km/h). If you
try to shift down into FIRST (1) at excessive vehicle
speeds, the shift lever will not move into the FIRST (1)
position until vehicle speed is reduced.SECOND (2): Press the clutch pedal and shift into
SECOND (2). Then, slowly let up on the clutch pedal as
you press the accelerator pedal.
You can shift into SECOND (2) when you're going less
than 20 mph (32 km/h). If you've come to a complete
stop and it's hard to shift into SECOND (2), put the shift
lever into NEUTRAL (N) and let up on the clutch.
Press the clutch pedal back down. Then shift into
SECOND (2). If you try to downshift into SECOND (2)
at excessive vehicle speeds, the shift lever will not move
into the SECOND (2) position until the vehicle speed
is reduced.
THIRD (3): Press the clutch pedal and shift into
THIRD (3). Then, slowly let up on the clutch pedal as
you press the accelerator pedal.
FOURTH (4) and FIFTH (5): Shift into the higher
forward gears the same way you do for THIRD (3).
Slowly let up on the clutch pedal as you press the
accelerator pedal.
To stop, let up on the accelerator pedal and press the
brake pedal. Just before the vehicle stops, press the
clutch pedal and the brake pedal, and shift to
NEUTRAL (N).

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2-20
NEUTRAL (N): Use this position when you start or
idle your engine.
REVERSE (R): To back up, first press down the clutch
pedal. Wait about five seconds for the internal parts to
stop spinning, and then shift into REVERSE (R).
Let up on the clutch pedal slowly while pressing the
accelerator pedal.
NOTICE:
Shift to REVERSE (R) only after your vehicle is
stopped. Shifting to REVERSE (R) while your
vehicle is moving could damage your transmission.
Also, use REVERSE (R), along with the parking brake,
when turning off your engine and parking your vehicle.
Shift Speeds
CAUTION:
If you skip more than one gear when you
downshift, you could lose control of your vehicle.
You could injure yourself or others. Don't shift
down more than one gear at a time when you
down shift.
If your speed drops below 20 mph (32 km/h), or if the
engine is not running smoothly, you should downshift to
the next lower gear. You may have to downshift two or
more gears to keep the engine running smoothly or for
good performance.

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2-23
4-Wheel High (4H): This setting engages your front
axle to help drive your vehicle. Use 4H when you need
extra traction and in most off
-road situations.
CAUTION:
Shifting the transfer case to NEUTRAL (N) can
cause your vehicle to roll even if the transmission
is in PARK (P), or if you have a manual
transmission, even if you are in gear. You or
someone else could be seriously injured. Be sure
to set the parking brake before placing the
transfer case in NEUTRAL (N). See ªParking
Brakeº in the Index.
NEUTRAL (N): Shift to this setting only when your
vehicle needs to be towed or when using a power
take
-off.
4
-Wheel Low (4L): This setting also engages your
front axle to give you extra power and also gives you a
higher driveline ratio. It should be used only for
off
-road driving.
You can shift from 2
-WHEEL HIGH (2H) to
4
-WHEEL HIGH (4H) or from 4-WHEEL HIGH (4H)
to 2
-WHEEL HIGH (2H) while the vehicle is moving.Your front axle will engage faster if you take your foot
off the accelerator for a few seconds after you shift. In
extremely cold weather, it may be necessary to stop or
slow the vehicle to shift into 4
-WHEEL HIGH (4H).
To shift into or out of 4
-WHEEL LOW (4L) or
NEUTRAL (N):
1. Slow the vehicle to a roll, about 1 to 3 mph
(2 to 5 km/h) and shift an automatic transmission
into NEUTRAL (N), or with a manual transmission,
press the clutch pedal.
2. Shift the transfer case shift lever in one
continuous motion.
Don't pause in NEUTRAL (N) as you shift the transfer
case into 4
-WHEEL LOW (4L), or your gears
could clash.
Remember that driving in 4
-WHEEL HIGH (4H) or
4
-WHEEL LOW (4L) may reduce fuel economy. Also,
driving in four
-wheel drive on dry pavement could
cause your tires to wear faster and make your transfer
case harder to shift and run noisier.
When your headlamps or parking lamps are on, rotate the
thumb wheel next to the headlamp switch up to brighten
or down to dim your transfer case indicator light.

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4-20
Q:What should I do if my vehicle stalls, or is about
to stall, and I can't make it up the hill?
A:If this happens, there are some things you should
do, and there are some things you must not do.
First, here's what you should do:

Push the brake pedal to stop the vehicle and keep it
from rolling backwards. Also, apply the parking brake.

If your engine is still running, shift the transmission
to REVERSE (R), release the parking brake, and
slowly back down the hill in REVERSE (R).

If your engine has stopped running, you'll need to
restart it. With the brake pedal pressed and the
parking brake still applied, shift the transmission to
PARK (P) (or, shift to NEUTRAL (N) if your
vehicle has a manual transmission) and restart the
engine. Then, shift to REVERSE (R), release the
parking brake, and slowly back down the hill as
straight as possible in REVERSE (R).

As you are backing down the hill, put your left hand
on the steering wheel at the 12 o'clock position. This
way, you'll be able to tell if your wheels are straight
and maneuver as you back down. It's best that youback down the hill with your wheels straight rather
than in the left or right direction. Turning the wheel
too far to the left or right will increase the possibility
of a rollover.
Here are some things you must not do if you stall,
or are about to stall, when going up a hill.

Never attempt to prevent a stall by shifting into
NEUTRAL (N) (or depressing the clutch, if you
have a manual transmission) to ªrev
-upº the engine
and regain forward momentum. This won't work.
Your vehicle will roll backwards very quickly and
you could go out of control.
Instead, apply the regular brake to stop the vehicle. Then
apply the parking brake. Shift to REVERSE (R), release
the parking brake, and slowly back straight down.

Never attempt to turn around if you are about to stall
when going up a hill. If the hill is steep enough to
stall your vehicle, it's steep enough to cause you to
roll over if you turn around. If you can't make it up
the hill, you must back straight down the hill.

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4-22 Driving Downhill
When off-roading takes you downhill, you'll want to
consider a number of things:

How steep is the downhill? Will I be able to maintain
vehicle control?

What's the surface like? Smooth? Rough? Slippery?
Hard
-packed dirt? Gravel?

Are there hidden surface obstacles? Ruts?
Logs? Boulders?

What's at the bottom of the hill? Is there a hidden
creek bank or even a river bottom with large rocks?
If you decide you can go down a hill safely, then try to
keep your vehicle headed straight down, and use a low
gear. This way, engine drag can help your brakes and
they won't have to do all the work. Descend slowly,
keeping your vehicle under control at all times.
CAUTION:
Heavy braking when going down a hill can cause
your brakes to overheat and fade. This could
cause loss of control and a serious accident. Apply
the brakes lightly when descending a hill and use
a low gear to keep vehicle speed under control.
Q:Are there some things I should not do when
driving down a hill?
A:Yes! These are important because if you
ignore them you could lose control and have
a serious accident.

When driving downhill, avoid turns that take you
across the incline of the hill. A hill that's not too
steep to drive down may be too steep to drive across.
You could roll over if you don't drive straight down.

Never go downhill with the transmission in
NEUTRAL (N), or with the clutch pedal depressed
in a manual shift. This is called ªfree
-wheeling.º
Your brakes will have to do all the work and could
overheat and fade.

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4-62
To engage a PTO:
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL (N).
4. Engage the PTO.
NOTICE:
Using a PTO for more than four hours without
driving your vehicle can damage the transfer case
or transmission. If using a PTO for more than
four hours without driving your vehicle, drive
your vehicle for a while to allow the transfer case
and transmission to cool.
If you are going to drive the vehicle, shift the
transfer case into the range you want (if you have
four
-wheel drive). Then shift the transmission into
the gear you want, apply the regular brakes and
release the parking brake.
5. Release the clutch (and the regular brakes) as you
normally would. When you release the clutch, the
PTO will start.To engage a PTO while the vehicle is moving:
1. Hold the clutch pedal down.
2. Shift the transmission into NEUTRAL (N).
3. Engage the PTO.
4. Shift the transmission into the gear you want.
5. Release the clutch as you normally would. When you
release the clutch, the PTO will start.
Using a Transfer Case Mounted Power
Take-Off (Manual Transmission)
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transfer case into NEUTRAL (N).
4. If the vehicle will remain in the same place, shift the
transmission into the highest gear.
5. Engage the PTO.
If you are going to drive the vehicle, shift the
transmission into the gear you want. Then shift the
transfer case into the range you want, apply the
regular brakes and release the parking brake.
6. Release the clutch (and the regular brakes) as you
normally would. When you release the clutch, the
PTO will start.

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5-19
Engine Fan Noise
Your vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions, the fan is spinning slower and the clutch is
not fully engaged. This improves fuel economy and
reduces fan noise. Under heavy vehicle loading, trailer
towing and/or high outside temperatures, the fan speed
increases as the clutch more fully engages. So you may
hear an increase in fan noise. This is normal and should
not be mistaken as the transmission slipping or making
extra shifts. It is merely the cooling system functioning
properly. The fan will slow down when additional
cooling is not required and the clutch disengages.
You may also hear this fan noise when you start
the engine. It will go away as the fan clutch
partially disengages.
If a Tire Goes Flat
It's unusual for a tire to ªblow outº while you're driving,
especially if you maintain your tires properly. If air goes
out of a tire, it's much more likely to leak out slowly.
But if you should ever have a ªblowout,º here are a few
tips about what to expect and what to do:
If a front tire fails, the flat tire will create a drag that
pulls the vehicle toward that side. Take your foot off the
accelerator pedal and grip the steering wheel firmly.
Steer to maintain lane position, and then gently brake to
a stop well out of the traffic lane.
A rear blowout, particularly on a curve, acts much like a
skid and may require the same correction you'd use in a
skid. In any rear blowout, remove your foot from the
accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop
-- well off the road if possible.
If a tire goes flat, the next part shows how to use your
jacking equipment to change a flat tire safely.