2001 GMC SIERRA automatic transmission

4-46 Four-Wheel-Drive Vehicles
CAUTION:
Shifting the transfer case into NEUTRAL can
cause your vehicle to roll even if the transmission
is in PARK (P), for an automatic transmission,
or if your vehicle is in gear, for a manual
transmission. You or others could be injured.
Make sure the parking brake is firmly set before
you shift the transfer case into NEUTRAL.
Use the following procedure to correctly tow your
vehicle on all four wheels:
1. Firmly set the parking brake.
2. Shift an automatic transmission to PARK (P),
or a manual transmission to FIRST (1).
3. Securely attach the vehicle being towed to the
tow vehicle.
4. Shift the transfer case to NEUTRAL (N).
See ªFour
-Wheel Driveº in the Index for the
proper procedure to select the neutral position for
your vehicle.
5. Release the parking brake only after the vehicle
being towed is firmly attached to the towing vehicle.
6. Turn the ignition to OFF. The OFF position unlocks
the steering column and reduces battery drain as long
as the IGN 0 fuse is removed. Unlocking the steering
column will allow the proper movement of the front
wheels and tires during towing.

4-58

Then, during the first 500 miles (800 km) that you
tow a trailer, don't drive over 50 mph (80 km/h) and
don't make starts at full throttle. This helps your
engine and other parts of your vehicle wear in at the
heavier loads.

If you have an automatic transmission, you can
tow in DRIVE (D). You may want to shift the
transmission to THIRD (3) or, if necessary, a lower
gear selection if the transmission shifts too often
(e.g., under heavy loads and/or hilly conditions).
If you have a manual transmission and you are
towing a trailer, it's better not to use FIFTH (5)
gear. Just drive in FOURTH (4) gear (or, as you
need to, a lower gear). See ªTow/Haul Modeº
in the Index.
Three important considerations have to do with weight:

the weight of the trailer,

the weight of the trailer tongue

and the weight on your vehicle's tires.Tow/Haul Mode (If Equipped)
Tow/haul is a feature on automatic transmission
equipped vehicles that assists when pulling a heavy
trailer or a large or heavy load. The purpose of the
tow/haul mode is to:

Reduce the frequency and improve the predictability
of transmission shifts when pulling a heavy trailer
or a large or heavy load.

Provide the same solid shift feel when pulling a
heavy trailer or a large or heavy load as when the
vehicle is unloaded.

Improve control of vehicle speed while requiring
less throttle pedal activity when pulling a heavy
trailer or a large or heavy load.
Automatic transmission equipped vehicles are provided
with a button at the end of the shift lever which when
pressed enables tow/haul. When the button is pressed,
a light on the instrument panel will illuminate to indicate
that tow/haul has been selected. Tow/haul may be turned
off by pressing the button again, at which time the
indicator light on the instrument panel will turn off.
The vehicle will automatically turn off tow/haul every
time it is started.

4-75 Turn Signals When Towing a Trailer
The arrows on your instrument panel will flash
whenever you signal a turn or lane change. Properly
hooked up, the trailer lamps will also flash, telling other
drivers you're about to turn, change lanes or stop.
When towing a trailer, the arrows on your instrument
panel will flash for turns even if the bulbs on the trailer
are burned out. Thus, you may think drivers behind you
are seeing your signal when they are not. It's important
to check occasionally to be sure the trailer bulbs are
still working.
Driving On Grades
Reduce speed and shift to a lower gear before you start
down a long or steep downgrade. If you don't shift
down, you might have to use your brakes so much that
they would get hot and no longer work well.
If you have an automatic transmission, you can tow in
DRIVE (D). You may want to shift the transmission
to THIRD (3) or, if necessary, a lower gear selection if
the transmission shifts too often (e.g., under heavy loads
and/or hilly conditions).You may also want to activate the tow/haul mode if the
transmission shifts too often. See ªTow/Haul Modeº in
the Index.
If you have a 5
-speed manual transmission and you are
towing a trailer, it's better not to use FIFTH (5) gear.
Just drive in FOURTH (4) gear (or, as you need to,
a lower gear).
If you have a 6
-speed manual transmission and you
are towing a trailer, it's better not to use SIXTH (6)
gear. Drive in FIFTH (5) gear (or, as you need to,
a lower gear).
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a
lower temperature than at normal altitudes. If you turn
your engine off immediately after towing at high altitude
on steep uphill grades, your vehicle may show signs
similar to engine overheating. To avoid this, let the
engine run while parked (preferably on level ground)
with the automatic transmission in PARK (P) (or the
manual transmission out of gear and the parking brake
applied) for a few minutes before turning the engine off.
If you do get the overheat warning, see ªEngine
Overheatingº in the Index.

4-76 Parking on Hills
CAUTION:
You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People can
be injured, and both your vehicle and the trailer
can be damaged.
But if you ever have to park your rig on a hill, here's
how to do it:
1. Apply your regular brakes, but don't shift into
PARK (P) yet for an automatic transmission,
or into gear for a manual transmission.
2. Have someone place chocks under the trailer wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
parking brake and shift into PARK (P) for an
automatic transmission, or REVERSE (R) for a
manual transmission.5. If you have a four
-wheel-drive vehicle, be sure
the transfer case is in a drive gear and not in
NEUTRAL (N).
6. Release the regular brakes.
CAUTION:
It can be 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.
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, use the
steps that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four-wheel drive vehicles
is in NEUTRAL, your vehicle will be free to roll,
even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not
in NEUTRAL.

4-77 When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:

Start your engine;

Shift into a gear; and

Release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when you're
pulling a trailer. See the Maintenance Schedule for
more on this. Things that are especially important
in trailer operation are automatic transmission fluid
(don't overfill), engine oil, axle lubricant, belt, cooling
system and brake system. Each of these is covered in
this manual, and the Index will help you find them
quickly. If you're trailering, it's a good idea to review
these sections before you start your trip.
Check periodically to see that all hitch nuts and
bolts are tight.
Trailer Wiring Harness
Your vehicle is equipped with one of the following
wiring harnesses for towing a trailer or hauling a
slide
-in camper.
Basic Trailer Wiring Package
All regular, extended cab crew cab pickups have a
six
-wire trailer towing harness.
The six-wire harness is located at the rear of the vehicle
and is tied to the vehicle's frame. The harness requires
the installation of a trailer
-wiring harness connector,
which is available through your dealer.

4-82 Power Take-Off (PTO) (If Equipped)
NOTICE:
If you have a PTO that will exceed 35 hp installed on
your vehicle, it could damage the transfer case or
transmission. When having a PTO installed on your
vehicle, make sure that it will not exceed 35 hp.
Before using a PTO, refer to the manufacturer's or
installer's instructions.
NOTICE:
Using a PTO while operating in one place before
the vehicle has reached normal operating
temperature can damage the transfer case or
transmission. If you will be using the PTO while
operating in one place, drive and warm up the
vehicle before using the PTO.
To engage a PTO on a vehicle with a
manual transmission:
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL (N).
4. Engage the PTO. Refer to the manufacturer's
or installer's for instructions on electrically
engaged PTOs.
5. For mobile operations, shift the transmission into
the gear you want, apply the regular brakes and
release the parking brake. For stationary operations,
leave the parking brake applied.
6. Release the clutch and regular brakes as you
normally would. When the clutch is released,
the PTO will start.
7. Turn the PTO rotary switch to ON.
To engage a PTO on a vehicle with an
automatic transmission:
1. Engine speed must be less than 1000 rpm.
2. Turn the PTO rotary switch ON.

5-4
2. Get the vehicles close enough so the jumper cables
can reach, but be sure the vehicles aren't touching
each other. If they are, it could cause a ground
connection you don't want. You wouldn't be able
to start your vehicle, and the bad grounding could
damage the electrical systems.
To avoid the possibility of the vehicles rolling, set the
parking brake firmly on both vehicles involved in the
jump start procedure. Put an automatic transmission in
PARK (P) or a manual transmission in NEUTRAL (N).
If you have a four
-wheel-drive vehicle, be sure the
transfer case is not in NEUTRAL (N).
3. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or accessory power outlets. Turn off all lamps
that aren't needed as well as radios. This will avoid
sparks and help save both batteries. In addition,
it could save your radio!
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
4. Open the hoods and locate the positive (+) and
negative (
-) terminal locations on the other vehicle.
Your vehicle has a remote positive (+) jump starting
terminal and a remote negative (
-) jump starting
terminal. The remote positive (+) terminal is located
behind a red plastic cover near the engine accessory
drive bracket. To uncover the remote positive (+)
terminal, open the red plastic cover.
On all V8 gasoline and diesel engines, the remote
negative (
-) terminal is located on the engine
accessory drive bracket. This is marked ªGNDº on
V8 engines. On V6 engines, the remote negative (
-)
terminal is located on a tab attached to the engine
accessory drive bracket where it is marked ªGNDº.
You should always use the remote positive (+)
and the remote negative (
-) terminals instead of
the positive (+) and negative (
-) terminals on
your battery.

5-10 If No Steam Is Coming From Your Engine
If you get an engine overheat warning but see or hear no
steam, the problem may not be too serious. Sometimes
the engine can get a little too hot when you:

Climb a long hill on a hot day.

Stop after high
-speed driving.

Idle for long periods in traffic.

Tow a trailer. See ªDriving on Gradesº in the Index.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. If you have an air conditioner and it's on, turn it off.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
3. If you're in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
-- DRIVE (D) for automatic transmissions.If you no longer have the overheat warning, you
can drive. Just to be safe, drive slower for about
10 minutes. If the warning doesn't come back on,
you can drive normally.
If the warning continues, pull over, stop, and park
your vehicle right away.
If there's still no sign of steam, push down the
accelerator until the engine speed is about twice as fast
as normal idle speed for at least three minutes while
you're parked. If you still have the warning, turn off
the engine and get everyone out of the vehicle until it
cools down. Also, see ªOverheated Engine Protection
Operating Modeº listed previously in this section.
You may decide not to lift the hood but to get service
help right away.