Hummer H2. Manual — part 32

BASIC CLUTCH TROUBLE SHOOTING CHART

unique situation or individual vehicle configuration. The purpose of this Trouble
Shooting information is to provide a list of common causes to problem
symptoms. For model-specific Trouble Shooting, refer to SUBJECT,
DIAGNOSTIC, or TESTING articles available in the section(s) you are accessing.

CONDITION & POSSIBLE CAUSE

CORRECTION

Chattering or Grabbing

Incorrect clutch adjustment

Adjust clutch

Oil, grease or glaze on facings

Disassemble and clean or replace

Loose "U" joint flange

See DRIVE AXLES article

Worn input shaft spline

Replace input shaft

Binding pressure plate

Replace pressure plate

Binding release lever

See CLUTCH article

Binding clutch disc hub

Replace clutch disc

Unequal pressure plate contact

Replace worn/misaligned components

Loose/bent clutch disc

Replace clutch disc

Incorrect transmission alignment

Realign transmission

Worn pressure plate, disc or flywheel

Replace damaged components

Broken or weak pressure springs

Replace pressure plate

Sticking clutch pedal

Lubricate clutch pedal & linkage

Incorrect clutch disc facing

Replace clutch disc

Engine loose in chassis

Tighten all mounting bolts

Failure to Release

Oil or grease on clutch facings

Clean or replace clutch clutch disc

Incorrect release lever or pedal
adjustment

See CLUTCH article

Worn or broken clutch facings

Replace clutch disc

Bent clutch disc or pressure plate

Replace damaged components

Clutch disc hub binding on input shaft

Clean or replace clutch disc and/or input

shaft

Binding pilot bearing

Replace pilot bearing

Sticking release bearing sleeve

Replace release bearing and/or sleeve

Binding clutch cable

See CLUTCH article

Defective clutch master

Replace master cylinder

Defective clutch slave

Replace slave cylinder

Air in hydraulic system

Bleed hydraulic system

Rattling

Weak or broken release lever spring

Replace spring and check alignment

Damaged pressure plate

Replace pressure plate

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

Broken clutch return spring

Replace return spring

Worn splines on clutch disc or input
shaft

Replace clutch disc and/or input shaft

Worn clutch release bearing

Replace release bearing

Dry or worn pilot bearing

Lubricate or replace pilot bearing

Unequal release lever contact

Align or replace release lever

Incorrect pedal free play

Adjust free play

Warped or damaged clutch disc

Replace damaged components

Slipping

Pressure springs worn or

Release pressure plate

Oily, greasy or worn facings

Clean or replace clutch disc

Incorrect clutch alignment

Realign clutch assembly

Warped clutch disc or pressure plate

Replace damaged components

Binding release levers or clutch pedal

Lubricate and/or replace release components

Squeaking

Worn or damaged release

Replace release bearing

Dry or worn pilot or release bearing

Lubricate or replace assembly

Pilot bearing turning in crankshaft

Replace pilot bearing and/or crankshaft

Worn input shaft bearing

Replace bearing and seal

Incorrect transmission alignment

Realign transmission

Dry release fork between pivot

Lubricate release fork and pivot

Heavy and/or Stiff Pedal

Sticking release bearing sleeve

Replace release bearing and/or sleeve

Dry or binding clutch pedal hub

Lubricate and align components

Floor mat interference with pedal

Lay mat flat in proper area

Dry or binding ball/fork pivots

Lubricate and align components

Faulty clutch cable

Replace clutch cable

Noisy Clutch Pedal

Faulty interlock switch

Replace interlock switch

Self-adjuster ratchet noise

Lubricate or replace self-adjuster

Speed control interlock switch

Lubricate or replace interlock switch

Clutch Pedal Sticks Down

Binding clutch cable

See CLUTCH article

Springs weak in pressure plate

Replace pressure plate

Binding in clutch linkage

Lubricate and free linkage

Noisy

Dry release bearing

Lubricate or replace release bearing

Dry or worn pilot bearing

Lubricate or replace bearing

Worn input shaft bearing

Replace bearing

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

DRIVE AXLE - NOISE DIAGNOSIS

Unrelated Noises

Some driveline trouble symptoms are also common to the engine, transmission, wheel bearings, tires, and other
parts of the vehicle. Ensure cause of trouble actually is in the drive axle before adjusting, repairing, or replacing
any of its parts.

Non-Drive Axle Noises

A few conditions can sound just like drive axle noise and have to be considered in pre-diagnosis. The 4 most
common noises are exhaust, tires, CV/universal joints and wheel trim rings.

In certain conditions, the pitch of the exhaust gases may e gear whine. At other times, it may be mistaken for a
wheel bearing rumble.

Tires, especially radial and snow, can have a high-pitched tread whine or roar, similar to gear noise. Also, some
non-standard tires with an unusual tread construction may emit a roar or whine.

Defective CV/universal joints may cause clicking noises or excessive driveline play that can be improperly
diagnosed as drive axle problems.

Trim and moldings also can cause a whistling or whining noise. Ensure none of these components are causing
the noise before disassembling the drive axle.

Gear Noise

A "howling" or "whining" noise from the ring and pinion gear can be caused by an improper gear pattern, gear
damage, or improper bearing preload. It can occur at various speeds and driving conditions, or it can be
continuous.

Before disassembling axle to diagnose and correct gear ke sure that tires, exhaust, and vehicle trim have been
checked as possible causes.

Chuckle

This is a particular rattling noise that sounds like a stick against the spokes of a spinning bicycle wheel. It
occurs while decelerating from 40 MPH and usually can be heard until vehicle comes to a complete stop. The
frequency varies with the speed of the vehicle.

Transmission Click

Weak springs in pressure

Replace pressure plate plate

Release fork loose on ball stud

Replace release fork and/or ball stud

Oil on clutch disc damper

Replace clutch disc

Broken spring in slave cylinder

Replace slave cylinder

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures

A chuckle that occurs on the driving phase is usually caused ive clearance due to differential gear wear, or by a
damaged tooth on the coast side of the pinion or ring gear. Even a very small tooth nick or a ridge on the edge
of a gear tooth is enough the cause the noise.

This condition can be corrected simply by cleaning the gear tooth nick or ridge with a small grinding wheel. If
either gear is damaged or scored badly, the gear set must be replaced. If metal has broken loose, the carrier and
housing must be cleaned to remove particles that could cause damage.

Knock

This is very similar to a chuckle, though it may be louder, and occur on acceleration or deceleration. Knock can
be caused by a gear tooth that is damaged on the drive side of the ring and pinion gears. Ring gear bolts that are
hitting the carrier casting can cause knock. Knock can also be due to excessive end play in the axle shafts.

Clunk

Clunk is a metallic noise heard when an automatic transmission is engaged in Reverse or Drive, or when throttle
is applied or released. It is caused by backlash somewhere in the driveline, but not necessarily in the axle. To
determine whether driveline clunk is caused by the axle, check the total axle backlash as follows:

1. Raise vehicle on a frame or twinpost hoist so that drive wheels are free. Clamp a bar between axle

companion flange and a part of the frame or body so that flange cannot move.

2. On conventional drive axles, lock the left wheel to keep it from turning. On all models, turn the right

wheel slowly until it is felt to be in Drive condition. Hold a chalk marker on side of tire about 12" from
center of wheel. Turn wheel in the opposite direction until it is again felt to be in Drive condition.

3. Measure the length of the chalk mark, which is the total axle backlash. If backlash is one inch or less,

drive axle is not the source of clunk noise.

Bearing Whine

Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by malfunctioning pinion
bearings. Pinion bearings operate at drive shaft speed. Roller wheel bearings may whine in a similar manner if
they run completely dry of lubricant. Bearing noise will occur at all driving speeds. This distinguishes it from
gear whine, which usually comes and goes as speed changes.

Bearing Rumble

Bearing rumble sounds like marbles being tumbled. It is usually caused by a malfunctioning wheel bearing. The
lower pitch is because the wheel bearing turns at only about 1/3 of drive shaft speed.

Chatter On Turns

This is a condition where the entire front or rear of vehicle vibrates when vehicle is moving. The vibration is
plainly felt as well as heard. Extra differential thrust washers installed during axle repair can cause a condition
of partial lock-up that creates this chatter.

Axle Shaft Noise

1998 Chevrolet Pickup C1500

GENERAL INFORMATION Trouble Shooting - Basic Procedures