1994 GMC SIERRA service

Air Cleaner
Refer to the
Maintenance Schedule
to determine when to
replace the air filter.
See “Scheduled
Maintenance Services” in the Index.
NOTICE:
If the air cleaner is off, a backfire can cause a damaging engine
fire. And, dirt can easily get into your engine, which will d\
amage
it. Always have the air cleaner in place when you’re drivin\
g.
6-29
ProCarManuals.com

.-. -1 To remove the air
cleaner filter on
a gas
engine or a 6.5 liter
naturally aspirated
diesel,
turn the wing
nuts to the left.
Remove the cover and
change the filter.
Then, unhook the
cover retaining clips
and push the rear
of
the cover toward the
engine.
Automatic Transmission Nuid
When to Check and Change
A good time to check your automatic transmission fluid level is when the
engine oil is changed. Refer
to the Maintenance Schedule to determine
when to change your fluid. See “Scheduled Maintenance Services”
in the
Index.
How to Check
Because this operation can be a little difficult, you may choose to have this
done at
a GM dealership Service Department.
If you do it yourself, be SLIK to follow all the instructions here, or you could
get a false reading on the dipstick.
6 - 30
ProCarManuals.com

How to Add Fluid
Refer to the Maintenance Schedule to determine what kind of transmission
fluid
to use. See “Recommended Fluids and Lubricants” in the Index.
If the fluid level is low, add
only enough of the proper fluid to bring the
level up to the COLD area for a cold check or the HOT area for a hot check.
It doesn’t take much tluid, generally less than a pint. Don’t overfill. We
recommend you use only fluid labeled DEXRON@-111 or DEXRON@-IIE,
because fluids with that label are made especially for your automatic
transmission. Damage caused by fluid other than
DEXRON@-Ill or
DEXRON@-IIE is not covered by your new vehicle warranty.
After adding fluid, recheck the fluid level as described under “How to
Check.”
When the correct fluid level is obtained, push the dipstick back in all
the way; then flip the handle down to lock the dipstick in place.
Manual Fluid
When to Check
A good time to have it checked is when the engine oil is changed. However,
the fluid
in your manual transmission doesn’t require changing.
How to Check
Because this operation can be a little difficult, you may choose to have this
done at a
GM dealership Service Department.
If you do it yourself, be sure to follow all the instructions here, or you could
get
a false reading.
NOTICE:
Too much or too little fluid can damage your transmission. Too
much can mean that some of the fluid could come out and fall on
hot engine parts or exhaust system, starting a fire. Be sure to get
an accurate reading if
you check your transmission fluid.
Check the fluid level only when your engine is off, the vehicle is parked on
a level place and the transmission is cool enough for you to rest your fingers
on the transmission case.
6-33
ProCarManuals.com

When to Check and What to Use
Refer to the
Maintenance Schedule
to determine how
often you should
check
the fluid level
in your clutch master
cylinder reservoir and
for the proper fluid.
See “Owner Checks and Services” and “Recommended Fluids and
Lubricants”
in the Index.
How to check
The proper fluid should be ridded if the level does not reach the bottom of
the diaphragm when it’s
in place in the reservoir. See the instructions on the
reservoir cap.
Hydraulic Clutch Grease Fitting
If you have a five speed manual transmission with deep low (RPO MT8), a
grease fitting is located on the clutch housing for lubricating the clutch fork
ball stud. See your Maintenance Schedule for when to lubricate the clutch
housing. See “Recommended Fluids and Lubricants”
in the Index for the
proper lubricant to
use.
Be sure not to over-fill because you could damage your clutch.
Rear Axle
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine how often to check the
lubricant and when to change
it. See “Scheduled Maintenance Services” in
the Index.
6-35
ProCarManuals.com

How to Check Lubricant
What to Use
- If the level is below
the
bottom of the filler
plug hole,
you’ll need
to add some lubricant.
Add enough lubricant
to raise the level to the
bottom of
the filler
plug hole.
Refer to the Maintenance Schedule to determine what kind
of lubricant to
use. See “Recommended Fluids and Lubricants” in the Index.
Front Axle
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine how often to check the
lubricant and when
to change it. See “Scheduled Maintenance Services” in
the Index.
How to Check Lubricant
If the level is below
the bottom of the filler
plug hole, you’ll need
to add some lubricant.
If the differential is at
operating temperature
(warm), add enough
lubricant
to raise the
level
to the bottom of
the filler plug hole.
If the differential is cold, add enough lubricant to raise the level to 1/2 inch
( 12 mm) below the filler plug hole.
6-37
ProCarManuals.com

Brake Wear
Your vehicle has front disc brakes and rear drum brakes. If you have a
C 3500 HD model, it has four-wheel disc brakes.
Disc brake pads have built-in wear indicators that make
a high-pitched
warning sound when the brake pads are worn and new pads are needed. The
sound may come and go or be heard
all the time your vehicle is moving
(except when you are pushing on the brake pedal firmly).
The brake wear warning sound means that sooner or later your
brakes won’t work well. That could lead to an accident.
When
you hear the brake wear warning sound, have your vehicle
serviced.
NOTICE:
Continuing to drive with worn-out brake pads could result in
costly brake repair.
Some driving conditions or climates may cause a brake squeal when the
brakes are first applied or lightly applied. This does not mean something is
wrong with your brakes.
If
you have rear drum brakes, they don’t have wear indicators, but if you
ever hear a rear brake rubbing noise, have
the rear brake linings inspected.
Also, the rear brake drums should be removed and inspected each time the
tires are removed for rotation or changing. When you have
the front brakes
replaced, have the rear brakes inspected, too.
Brake linings should always be replaced
as complete axle sets.
Brake Pedal Travel
See your dealer if the brake pedal does not return to normal height, or if
there is a rapid increase in pedal travel. This could be a sign of brake
trouble.
6-48
ProCarManuals.com

Brake Adjustment
Every time you make a brake stop, your disc brakes adjust for wear.
If your brake pedal goes down farther than normal, your rear drum brakes
may need adjustment. Adjust them by backing up and firmly applying
the
brakes a few times.
Replacing Brake System Parts
The braking system on a modern vehicle is complex. Its many parts have to
be of top quality and work well together if the vehicle is to have really good
braking. Vehicles we design and test have top-quality
GM brake parts in
them, as your vehicle does when it is new. When you replace parts of your
braking system
- for example, when your brake linings wear down and
you have to have new ones put
in - be sure you get new genuine GM
replacement parts. If you don’t, your brakes may no longer work properly.
For example,
if someone puts in brake linings that are wrong for your
vehicle, the balance between your front and rear brakes can change, for
the
worse. The braking performance you’ve come to expect can change in many
other ways if someone puts in the wrong replacement brake parts.
Other Maintenance Hems
Front Suspension and Steering Linkage
Your maintenance schedule will tell you how often to lubricate the fittings.
See “Recommended Fluids and Lubricants”
in the Index for the proper
lubricant to use.
Front Wheel Bearings
Your vehicle has front wheel bearings that must be cleaned and repacked.
Your maintenance schedule
will tell you how often this must be done.
Front Shock Absorbers
The front shock absorbers of your vehicle do many things. They help the
vehicle ride smoothly and also control
the travel of the suspension system.
When the shock absorbers are serviced, any replacement shock absorbers
must be
the same as the original equipment shock absorbers in both
extended length and strength.
NOTICE:
If you use shock absorbers that are not the same as the original
shock absorbers, the shock absorbers
or suspension system
could be damaged.
6-49
ProCarManuals.com

Exhaust System
To help prevent damage to your exhaust system, do not continue to drive
your vehicle
if you notice:
Engine misfiring
Loss of performance
0 Other unusual operating conditions
Have your engine and exhaust system serviced regularly.
Three- Way Catalytic Converter (gas engines)
Your vehicle’s three-way catalytic converter is designed to reduce the
pollutants
in your vehicle’s exhaust. Use only unleaded fuel in your vehicle.
If you use leaded fuel, you could damage your three-way catalytic converter
and other engine components.
Three- Way Catalytic Converter (diesel engines)
Your vehicle’s thre.e-way catalytic converter is designed to reduce the
particulates
in your vehicle’s exhaust. If your vehicles three-way catalytic
converter ever needs to be replaced,
it must be replaced with a three-way
catalytic converter intended for use with diesel engines
only.
Engine Control Module System
(All TBI equipped vehicles and diesel engine
vehicles below
8,500 Ibs. GVWR)
Gasoline Engines
This system has an oxygen sensor (02 ) that helps keep your engine’s
air-fuel mixture at
a proper level. Use only unleaded fuel in your vehicle. If
you use leaded fuel, you could damage your oxygen sensor (02) and
three-way catalytic converter.
Diesel Vehicles Below 8,500 LBS. GVWR
This system monitors engine speed and throttle position. It adjusts exhaust
gas recirculation to limit emissions.
6-64
ProCarManuals.com