1995 GMC SIERRA trailer

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 every day
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 partially 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 “blow out” 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 “blowout,” 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, 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.
5-25
ProCarManuals.com

NOTICE:
Use only engine oil with the American Petroleum Institute
Certified For Gasoline Engines “Starburst” symbol. Failure \
to
use the proper oil can result in engine damage not covered
by
your warranty.
GM Goodwrench@ oil (in Canada, GM Engine Oil) meets all the
requirements for your vehicle.
Engine Oil Additives
Don’t add anything to your oil. Your GM dealer is ready to advise if you
think something should be added.
When to Change Engine Oil
See if any one of these is true for you:
Most trips are less than 5 to 10 miles (8 to 16 km). This is particularly
important when outside temperatures are below freezing.
Most trips include extensive idling (such as frequent driving in stop and
go traffic).
Most trips are through dusty areas.
You operate your vehicle in dusty areas or off-road frequently.
You frequently tow a trailer.
If any one
of these is true for your vehicle, then you need to change your oil
and filter every
3,000 miles (5 000 km) or 3 months - whichever comes
first.
Light Duty Emissions:
If none of them is true, change the oil and filter every 7,500 miles (12 500
km) or 12 months - whichever comes first.
Heavy Duty Emissions:
If none of them is true, change the oil and filter every 6,000 miles (10 000
km) or 12 months - whichever comes first.
6-20
ProCarManuals.com

This doughnut-shaped logo (symbol) is used on most oil containers to help
you select the correct oil.
You should look for this
on the oil container, and use only those oils that
display the logo.
GM Goodwrench‘ oil (in Canada, GM Engine Oil) meets all the
requirements for your vehicle.
Engine Oil Additives
Don’t add anything to your oil. Your GM dealer is ready to advise if you
think something should be added.
When to Change Engine Oil
See if any one of these is true for you:
0 Most trips are less than 5 to IO miles (8 to 16 km). This is particularly
important when outside temperatures are below freezing.
0 Most trips include extensive idling (such as frequent driving in stop and
e 00 traffic).
0 You operate your vehicle in dusty areas or off-road frequently.
0 You frequently tow a trailer or use a carrier on top of your vehicle.
If any of these is true for your vehicle, then you need to change your oil and
filter every
2,500 miles (4 000 km) or 3 months - whichever comes first.
If none of them is true, change the oil and filter every
5,000 miles (8 000
km) or 12 months - whichever comes first.
What to Do with Used Oil
Did you know that used engine oil contains certain elements that may be
unhealthy for your skin and could even cause cancer? Don‘t let used oil stay
on your skin for very long. Clean your skin and nails with soap and water,
or
a good hand cleaner. Wash or properly throw away clothing or rags
containing used engine oil. (See the manufacturer’s warnings about the use
and disposal
of oil products.)
Used oil can be a real threat
to the environment. If you change your own oil,
be sure
to drain all free-flowing oil from the filter before disposal. Don’t
ever dispose of oil by putting it
in the trash, pouring it on the ground, into
sewers, or into streams or bodies of water. Instead, recycle
it by taking it to
a place that collects used oil. If you have a problem properly disposing of
your used oil, ask your dealer, a service station or a local recycling center
for help.
6-25
ProCarManuals.com

Wait at least 30 minutes before checking the transmission fluid level if you
have been driving:
When outside temperatures are above 90°F (32°C).
At high speed for quite a while.
In heavy traffic - especially in hot weather.
While pulling a trailer.
To get the right reading. the fluid should be at normal operating
temperature, which is 180°F to 200°F
(82°C to 93°C).
To check transmission fluid hot: Get the vehicle warmed up by driving
about
15 miles (24 km) when outside temperatures are above 50°F (10°C).
If it's colder than 50°F (lO"C), drive the vehicle in DRIVE (3) until the
engine temperature gage moves and then remains steady for ten minutes.
Then follow the hot check procedures.
To check transmission fluid cold: A cold check is made after the vehicle
has been sitting for eight hours or more
with the engine off and is used only
as a reference. Let the engine run at idle for five minutes if outside
temperatures are 50°F
(10°C) or more. If it's colder than 50°F (IOOC), you
may have to idle the engine longer. Should the fluid level be low during a
cold check, you
must perform a hot check before adding fluid. This will
give you a more accurate reading of the fluid level.
To check the fluid hot or cold
Park your vehicle on a level place. Keep the engine running.
With the parking brake applied, place the shift lever in PARK (P).
With your foot on the brake pedal, move the shift lever through each
gear range, pausing for about three seconds
in each range. Then,
position the shift lever
in PARK (P).
Let the engine run at idle for three minutes or more.
6-28
ProCarManuals.com

What to Use
Refer to the Maintenance Schedule to determine what kind of lubricant to
use. See “Recommended Fluids and Lubricants”
in the Index.
C3 (3500 H.D.) Trucks Equipped with Dana Rear Axle
Additional rear axle scheduled maintenance is required on 3500 H.D.
models equipped with Dana rear axles when they are driven under the
following conditions:
0 Extreme loading (at or near GVWR) or trailer towing, and:
Operation above 45 mph for extended periods of time
Vehicles used
in any of these conditions require the rear axle lubricant (SAE
8OW-90 - GL-5) be changed every 3 months or 3,000 miles, whichever
comes first.
To reduce required maintenance, SAE 75W-140 synthetic gear lubricant
may be used. With the use of synthetic
SAE 75W-140 lubricant, the fluid
change intervals may be increased to 30,000 miles. Before using SAE
75W-140, it is important to drain and flush the axle with clean mineral
based (non-synthetic) axle lubricant. Fluid capacity is 4.12 qts. (3.9L).
Four- Wheel Drive
Most lubricant checks in this section also apply to four-wheel-drive
vehicles. However, they have two additional systems that need lubrication.
Transfer Case
When to Check Lubricant
Refer to the Maintenance Schedule to determine how often to check the
lubricant. See “Periodic Maintenance Inspections”
in the Index.
6-33
ProCarManuals.com

Fuses and Circuit Breakers
The wiring circuits in your vehicle are protected from short circuits by a
combination of fuses, circuit breakers, and fusible thermal links
in the
wiring itself. This greatly reduces
the chance of fires caused by electrical
problems. See “Fuses and Circuit Breakers’’
in the Index for more
information.
Headlamps
The headlamp wiring is protected by a circuit breaker in the lamp switch.
An electrical overload will cause
the lamps to flicker on and off, or in some
cases to remain
off. If this happens, have your headlamp wiring checked
right away.
Windshield Wipers
The windshield wiper motor is protected by a clrculc DreaKer ana a ruse. 11
the motor overheats due to heavy snow, etc., the wiper will stop until the
motor cools. Although the circuit is protected from electrical overload,
overload due to heavy snow, etc., may cause wiper linkage damage. Always
clear ice and heavy snow from the the windshield before using the
windshield wipers. If the overload
is caused by some electrical problem and
not snow, etc., be sure
to get it fixed.
Power Windows and Other Power Options
Circuit breakers in the fuse panel protect the power windows and other
power accessories. When the current load is too heavy, the circuit breaker
opens and closes. This protects the circuit
until the current load returns to
normal or the problem is fixed.
Trailer Wiring Harness
The standard seven-wire trailer wiring harness is protected by an in-line
fuse in the battery feed wire. This fuse is near the junction block. See
“Trailer Wiring Harness” in the Index for more information.
6-79
ProCarManuals.com

If your engine has more than one emissions classification, the classification
is determined by the Gross Vehicle Weight Rating (GVWR) of your vehicle
as shown on the Certification Label. See “Loading Your Vehicle”
in the
Index.
Once you’ve determined your engine type and,
if necessary, emissions
classification, you’ll need to decide which of the two schedules is right for
your vehicle. See Definitions for Maintenance Schedule
I and Maintenance
Schedule
I1 following.
Schedule I Definition - Gasoline Engines With Light Duty
Emissions
Follow Maintenance Schedule I if any one of these is true for your vehicle:
iII Most trips are less than 5 to 10 miles (8 to 16 km). This is particularly
important when outside temperatures are below freezing.
0 Most trips include extensive idling (such as frequent driving in
stop-and-go traffic).
You operate your vehicle in dusty areas or off-road frequently.
0 You frequently tow a trailer.
Schedule
I should also be followed if the vehicle is used for delivery
service, police, taxi, or other commercial application.
Schedule I Intervals - Gasoline Engines With Light Duty
Emissions
Every
3,000 Miles (5 000 km) or 3 Months, Whichever Occurs First
Engine Oil and Filter Change
Chassis Lubrication
Drive Axle Service
At 6,000 Miles (10 000 km) - Then Every 12,000 Miles (25 000 km)
Tire Rotation
Every 75,000 Miles (25 000 km)
Air Cleaner Filter Inspection, if driving in dusty conditions
Front Wheel Bearing Repack
(or at each brake relining) (2WD Only)
7-4
ProCarManuals.com

Every 30,000 Miles (50 000 km)
Cooling System Service (or every 24 months)
Spark Plug Replacement
Fuel Filter Replacement
Air Cleaner Filter Replacement
Front Wheel Bearing Repack
Every 50,000 Miles (83 000 km)
Automatic Transmission Service (severe conditions only)
Every 60,000 Miles (100 000 km)
Spark Plug Wire Inspection
Engine Accessory Drive Belt Inspection
Fuel Tank,
Cap and Lines Inspection
Engine Timing Check
Schedule 1 Definition - Gasoline Engines With Heavy Duiy
Emissions
I
Follow Maintenance Schedule I if any one of these is true for your vehicle:
0 Most trips are less than 5 to 10 miles (8 to 16 km). This is particularly
important when outside temperatures are below freezing.
Most trips include extensive idling (such as frequent driving in stop and
go traffic).
You operate your vehicle in dusty areas or off-road frequently.
You frequently tow a trailer.
Schedule
I should also be followed if the vehicle is used for delivery
service, police, taxi, or other commercial application.
7-6
ProCarManuals.com