HET 4 CLUTCH Flashcards
190401A CLUTCH
Spring loaded clutches have three styles of spring, what are they?
Perpendicular, diaphragm and angle
What are the two types of spring clutches?
Push and Pull type
When the operator pushes the clutch pedal to the floorboard, is the clutch engaged or disengaged?
Disengaged
The springs in the clutch are held in the engage or disengaged position?
Engaged
Where are the pressure springs usually located?
between the clutch cover and pressure plate
When a spring-loaded clutch is engaged what happens to the clutch disc, pressure plate and flywheel friction surface?
The clutch disc is held tightly between the pressure plate and flywheel friction surfaces
True or False
In a spring-loaded clutch, when engaged two out of three components rotate together at the same speed?
FALSE all three components rotate together at the same speed
Pressure plate, clutch disc, flywheel friction surface
What dictates a clutch is a PUSH or PULL type?
The direction the release bearing is going
Pull-type clutches are used on what level of vehicles?
medium to heavy duty
The release bearing pushes or pulls on what part of the component?
Release levers
When the clutch disc is disengaged what moves together?
Clutch cover/pressure plate assembly rotates with the flywheel
When a clutch is getting ridden a lot what will wear?
a) flywheel
b) clutch disc
c) friction material
d) pressure plate
c) The clutch friction material - lining
Spring strength comes from what?
Its compression
When a spring has to travel further what happens to its pressure application ability?
it gets weaker
When adjusting clutch’s lever pivot point what are we adjusting?
The spring force available
Does free play become more or less when the clutch is worn severely?
Less free play
In medium - heavy duty truck, what is the common clutch type?
Pull type
What are two things that dictate if the clutch is a push or pull type?
Release bearing travel and release levers travel
What are the four ways to find the size of a clutch?
diameter of the disc
outside diameter of the clutch shaft
number of splines in the hub
number of dampening springs
Where is a flywheel mounted to making it run at engine speeds?
Crankshaft flange
What are two types of flywheels?
Flat and Countersunk
How many reservoirs does a hydraulic clutch master cylinder have?
ONE
If a hydraulic clutch actuation mechanism fails, what is the complaint?
Clutch will not disengage
What type of air is used in a air over hydraulic assist for clutch use?
compressed air
When an operator releases the pedal what position is the clutch in?
Engaged
What are the actuation mechanisms used for clutches?
Mechanical linkage
Hydraulic
Air over Hydraulic
In a vehicle where the transmission/engine are VERY far from the operator pedal, what actuation mechanism is used?
Hydraulic
or
Air over Hydraulic
If the engine/transmission is close to the operators clutch pedal, what actuation mechanism is most likely to be used?
Mechanical Linkage
If a clutch pedal linked to a mechanical linkage has lots of free play but the clutch is adjusted correctly, what is cause?
The bearings, rod end and/or bushings in the linkage are worn
Out of the three clutch actuation mechanisms, which is the least expensive?
Mechanical linkage
Flat flywheels are used on a single or a double disc clutch assembly?
Both
If there are air bubbles in the hydraulic clutch system, what is the operators complaint?
Spongy pedal
If a clutch pedal has excessive side to side movement, what should a tech be looking for as the cause?
Worn bushings in the pedal linkage
What are basic inspections on a hydraulic clutch that a technician can do?
Check lines for damage and wear
Check for leaks
Pedal movement/feel
Reservoir level and fluid condition
When installing a new master cylinder in a hydraulic clutch assembly what should be done FIRST?
Bench bleed the master cylinder
A rod end link is considered failed when what movement is felt?
The ball can move separately from the socket
What law is followed in hydraulics?
Pascall’s law
Do perpendicular spring clutches have helper springs?
NO
What spring clutch has helper springs?
Angle springs
In an air over hydraulic clutch mechanism, where do the clutch master cylinder send pressurized fluid to when the pedal is pushed on?
To the integral hydraulic cylinder
What is the air chamber’s default position in an air over hydraulic clutch mechanism?
Exhaust to atmospher
List the controlled and assist pressures in an air over hydraulic clutch mechanism?
Hydraulic - Control
Air - Assist
True or False
If clutch discs are the same size they can handle the same torque loads?
False, diameter is not the only thing that matters when rating a clutch disc
Do flywheels need to be measured for thickness and true rotation when replacing the clutch or troubleshooting a clutch fault?
Yes, its a wearable component
What drives the intermediate plate in a system with a countersunk flywheel system?
Flywheel
What is the point of an intermediate plate?
Additional friction surface
Clutch covers are usually made from?
Cast iron
or
Stamped steel
Which is better for heavy duty applications, cast iron clutch covers or stamped steel?
Cast iron is heavier and can absorb more heat
Why can a clutch design with 2 clutch discs handle more torque?
Larger surface area (double)
What are two PROs to stamped steel clutch covers?
Higher engine speeds and Lighter
Anything directly coupled to the flywheel/crank are considered what kind of member?
Driven or Drive
Drive
Anything directly coupled to the transmission is considered what kind of member?
Driven or Drive
Driven
Rigid clutch discs how is the lining connected to it?
Bonded or riveted
Where are rigid clutches used? What type of application?
Where there is a limit amount of engagement and disengagement occur
Dampened clutch discs are considered flexible or rigid?
Flexible
What is used on a dampened clutch disc to absorb torsional shock loads?
spring-loaded, limited-movement mechanism
What do dampened clutch discs do to service life of the clutch?
Extend clutch service life
What are the two types of clutch disc linings materials?
Organic and Ceramic
What clutch disc lining should be used where high heat will be encountered?
Ceramic
Organic clutch linings in CANADA are made with asbestos?
No, asbestos is not legal in Canada
BUT it can be used when manufactured in another country
In an NAO clutch disc lining what could be added to the material?
binders, resins, fillers, metallic particles
Is it more likely for a ceramic clutch disc lining to last longer than a organic clutch disc lining?
Yes
An intermediate plate is used when?
Two clutch discs are used
It is normal for the intermediate plate to be fastened tightly to the flywheel/clutch cover?
No, should have some movement
What component helps stop intermediate plate vibrations and reduce noise?
Anti-rattle springs
What could be driving an intermediate plate that is being driven by the clutch cover?
Drive Strap
A clutch that sounds like it is “rattling” when engaged could be a result of?
A broken dampening springs in the clutch disc
A clutch is starting to feel like its causing hard shifts, what could be the cause?
broken dampening springs in the clutch disc
If the pressure plate is moving towards the clutch cover where is it moving away from?
The flywheel (engine)
Does diaphragm clutch have more or less release levers compared to an angle spring style clutch?
diaphragm has More
What does the clutch pedal connect to push/pull the release bearing?
Yoke (release yoke)
How much gap should there be between the yoke and release bearing?
1/8”
Operator complains the clutch is feeling stiff or harder, what could be the cause?
Worn clutch disc
When you short stroke the clutch pedal while making a shift what will be the result?
Stress on the shift diodes (synchronizers) - premature failure
What generally causes premature failures of transmissions and clutches?
Abuse from operator
What can cause a failure of a self-adjuster in the clutch?
Contamination - tiny teeth
As a clutch wears what will need to be done to get free travel back?
Adjustment - manual
won’t need to be done if auto adjusters are installed
Which type of clutch can have an internal threaded ring that you must unlock first before adjusting the clutch?
Pull-type
True or False
All push-type clutches have self adjusting clutches?
FALSE
When does a clutch brake activate?
When the operator is shifting from neutral to first or reverse gear
What does a clutch brake prevent?
Gear teeth clash during gear selection
What is the purpose of the clutch brake?
To stop rotation of the transmission input shaft
True or False
Release bearings push up against the clutch brake when the clutch is disengaged?
True
At what point in clutch pedal travel should the clutch brake activated? (squeezed)
1/2”-1” from the floor (bottom of travel)
What can cause premature failure of the clutch brake?
contamination, improper use
Operator complains the truck is hard to get into 1st gear and reverse gear, what could be the cause?
Failed clutch brake
What is considered improper use of the clutch brake?
engaging the clutch brake while traveling in 2-6th gear
Do you need to replace the clutch to replace the clutch brake?
NO, clutch brake will have to be installed in two pieces
A multi piece clutch brake is split into halves?
No, has multiple friction discs and plates
When removing a clutch brake from the shaft what will need to be done?
the clutch brake will have to be split in half
A torque-limiting clutch brake has how many pieces?
one-piece
At what torque level will the torque-limiting clutch brake slip at?
A pre-determined torque load
If a clutch brake is able to slip what will happen to service life of the component?
service life will be extended
Is it common for medium-heavy duty trucks to have clutch brakes?
Yes highly common
What will prolong clutch service life?
regular inspection, adjustment, keep clean
If a flywheel has a deep gouge into it from a rock being dragging around, can it simply be machined/cut to refresh the face of the flywheel?
Depending on the depth of the cut, flywheel must be above minimum thickness
How many operators using a piece of equipment is preferred for prolonged service life of clutch components?
One operator using the piece of equipment
True or False
Its a good thing when oil gets inside the clutch housing?
False - clutch lining material will not do well if contaminated with oil
Where could the oil contamination in a clutch housing come from?
Rear main housing seal
During clutch slippage what is created?
HEAT
What usually needs to be removed to replace a clutch?
Transmission
When starting to move a vehicle with a heavy load what gear should be selected?
The lowest gear
If the clamp load is decreased on a clutch, what will be the result?
Slippage
Dragging clutch occurs when?
Clutch disc is not quickly freed from the flywheel or pressure plate when the pedal is depressed
What can a dragging clutch cause?
Gear clash - gear tooth damage - difficulty shifting
Describe free play
The amount of movement of the clutch pedal before resistance is encountered
ie. 1” (or manufacture spec)
Free play is also called?
Free pedal
What can cause chattering in a clutch?
Wear in external components
Over heating a clutch can do what to the clutch disc?
clutch disc can warp
Lubrication contamination of the clutch lining could give what symptom?
Chatting during engagement and disengagement
A glazed clutch disc that is worn in an unusual pattern could be caused by?
Lubrication contamination
If a clutch disc lining falls off due to a manufacture defect, what may the operator complaint be?
Noise in the rear end, transmission or u-joint
Confirm all clutch components are correct
It is not important to have balanced clutch components?
No, an imbalance can cause vibrations
What should be used when moving the heavy clutch over assembly away from the engine?
Two Long Guide Studs
What should be used to help control the clutch discs while the clutch is removed?
Clutch disc aligning tool
When removing clutch cover fasteners what should a technician be aware of?
removal pattern from manufacture spec
What are somethings a technician should do before removing transmissions/clutch components?
Clean the area and disconnect the battery
What must be done before setting the clutch free pedal?
Checked all of the external linkage for wear and signs of binding, must be properly lubricated
To check the flywheel bore runout what position does the dial-indicator need to be in?
90° to the surface
Is it possible for crankshaft end play to affect shifting?
Yes if it is out of allowable limits
pg 32 190401a
What is done to move the crankshaft to the limit of its travel?
A pry bar between the flywheel and flywheel housing
Why should you check crankshaft end play more than once?
To squeeze out oil film, giving a more accurate reading
What should be used to disassemble the pressure plate?
A press system (adapter)
What should be used to clean clutch components?
steam, water, brake cleaning solution
What should never be used to clean clutch components?
Grease, oil based products, varsol
An operator complains the clutch feels like it is dragging/grabbing. What could be the cause?
Flywheel face runout is beyond specs
EXAMPLE
Face runout measurement - first spot negative (-0.005”), next spot positive (+0.008”), what is total runout?
0.013” is total run out
add numbers together (positive and negative don’t count)
Before checking the flywheel housing face runout what must be checked?
Flywheel runout (face and bore)
What should be used to install a flywheel?
guide studs
What is the procedure for torquing a flywheel on?
Four step process 1/3, 2/3, full and recheck .
with recommended torque pattern
When installing a clutch with two clutch discs, what should the intermediate plate be contacting before installing the clutch assembly?
Both clutch disc friction surfaces
How can timing be verified on an unknown engine?
Steel rod in injector hole, dial indicator on the end of the rod. Bar engine over to find TDC
Manufactures do what to clutch facing to help with assembly?
Stamp identifying marks on facings, to indicate flywheel side
In a push-type clutch with a hydraulic master cylinder what needs to be done after the clutch has been adjusted?
Pushrods must be secured in the locked positions
What are some clearances that manufacturers might recommend to be checked? ( part a between part b)
- between yoke and release bearing
- between release bearing and release levels
- between rear of release bearing and front of clutch brake
How is clutch brake operation tested?
Vehicle stationary, engine running and the transmission is shifted from neutral to low and reverse gear
After a thorough road test and clutch is confirmed to operating correctly, the clutch free pedal has been rechecked. What should be communicated to the operator?
The clutch should be readjusted at the first oil change service interval
What is the operator complaint if the centrifugal force clutch fails in the engaged position?
Engine is hard to start
Drive component is always moving
What two forces do centrifugal clutches utilize?
Centrifugal force
Friction Force
What could cause a centrifugal force clutch to stay engaged?
Release/return springs have failed
At full load speed what position are the shoes in against the drum? What is the result?
Shoes are locked against drum and there is no slippage
What supports the load in a centrifugal force clutch assembly?
a) clutch material
b) bearings
c) shaft
d) weights
Bearings
Which component is spring controlled in a centrifugal force clutch?
Friction shoes
What tools are used to measure the warpage of a pressure plate or intermediate plate?
Straight edge
Feeler Gauge
Where can oil/grease contamination come from in a clutch?
Engine rear main oil seal (leaking), transmission input shaft oil seal(leaking), excessive grease used on the release bearing
Explain why a clutch release bearing is used?
A rotating release bearing will minimize wear of the release levers during engagement/disengagement process
In what applications would a rigid clutch disc be used?
Where limited amount of engagement and disengagement occur
Push type clutches are usually used on what class of vehicle?
light-medium duty
If a flywheel has some hot spotting can be it reused or it must be replaced?
If it can be resurfaced with machining it can be used - minimum thickness
Chattering clutches basic cause is from?
Partial engagement
What causes the MOST wear to a clutch friction disc?
Clutch slippage
Do engines and transmission need to have concentric alignment?
Yes
Internal plate is rattling (noisy) what can be done?
Anti-rattle springs could be used between the drive pins and intermediate plate drive slots
The springs inside a clutch friction disc are called?
Torsion Dampening springs
The cut out lines that are in a clutch friction disc can do what?
Help remove debris from wearing material
Help with cool down
Help with release, avoid friction disc from sticking
