clutch fundamentals and service Flashcards
what do spring loaded clutches allow
a drive unit to be connected to a driven unit
besides connecting two components together what do clutches also provide
a means of smoothly transmitting power during the engagement process and providing a means of temporarily disengaging an engine from a transmission
how is the clutch engaged or disengaged
through some sort of mechanical linkage or partial mechanical with hydraulic or an air/hydraulic pressure assist
how are spring loaded clutches applied and engaged
with some sort of spring located within the clutch assembly
the pressure springs can be what type of design
diaphragm, angled or perpendicular coil spring design
where are the pressure springs usually located
between the clutch cover and the pressure plate
what are the two types of spring clutches
push style and pull style
when the spring loaded clutch is engaged it is tightly between the
pressure plate and flywheel friction surfaces
when the clutch is engaged all three components ( engine, clutch and transmission ) will
rotate together at the same speed
what happens during the disengagement process
pressure springs are slightly compressed - clamping force is eliminated and the clutch disc is able to move freely of the flywheel and pressure plate friction surface -
what happens when the clutch is disengaged
the flywheel and clutch cover/pressure plate assembly will rotate at engine speed while the clutch disc remains stationary or rotates at transmission input shaft speed
where are push type clutches used
light to medium duty vehicles
how are push type clutches disengaged
as the operator moves the clutch pedal towards the floor a mechanical linkage system within the clutch continues the disengagement process
clutch release levers used in push-type clutches are attached to and located
within the clutch cover/pressure plate assembly
where are pull-type clutches used
in medium to heavy duty vehicles
when a pull type clutch assembly is disengaged the release bearing sleeve will
be pulled away from the flywheel
when is mechanical clutch actuation linkage usually used
when the engine, clutch, transmission and cab are in reasonably close proximity with space available
what are the benefits of mechanical linkage
relatively inexpensive, can operate with a certain amount of wear or damage and is fairly simple to repair and adjust
what are disadvantages of mechanical linkage
numerous wear points lubrication may be limited to major wear points pin and yokes may be exposed to road dirt and water causing accelerated wear
how are hydraulically activated clutches actuated
operator pushed the clutch pedal connected to a push rod connected to a single reservoir clutch master cylinder connected to a single piston slave cylinder by steel lines and flex lines
what are disadvantages to hydraulically actuated clutches
if a line breaks or there is air in the system clutch function will be lost
what are advantages to hydraulically actuated clutches
mounting versatility . ease of force application . easy access to the slave cylinder and master cylinder
why would air over hydraulic assist assembly be used when releasing a clutch
because the spring pressure in the clutch may be to great for operator foot pressure to overcome
how can clutch size be determined
diameter of the disc - outside diameter of the clutch shaft - number of splines in the hub - number of dampening springs
what are the main functions of the flywheel
to provide a flat smooth friction surface for one side of the clutch disc to work against and provide a bore with a bearing to pilot the transmission input shaft
why is the piloting feature in a flywheel or crankshaft critical to a clutch
because the inputshaft of the transmission that is piloted into the bore is used to center the clutch disc in relation to the pressure plate
what are the two types of flywheels
flat and countersunk
flat flywheels
combines two surfaces. the machined surface area where the clutch cover is fastened and the friction surface where the clutch disc will be positioned
flat fly wheels are suitable for
both single and double clutch disc assemblies
countersunk flywheels have
a recessed friction surface
the countersunk design allows for
a double clutch assembly to be used
what will having a double clutch assembly allow for
the handling of increased torque loads due to the increased friction surface
what is used to separate the clutch discs in a double clutch design
an intermediate plate that is driven by the flywheel or clutch cover between the two discs
what are the two types of clutch cover construction
cast iron and stamped steel
what are the advantages of cast iron clutch covers
can handle high heat and due to the ridged construction high torque loads
what are advantages of the stamped steel clutch covers
lighter design and allow for higher engine speeds to develop
pressure plates are typically constructed from
cast iron
where is the pressure plate located
in the clutch cover and is driven by the clutch cover during operation
perpendicular coil springs are
a series of coil springs standing at 90 degrees to the pressure plate
the springs keep the pressure plate in the
engaged position
angled coil springs are
a series of coiled springs at an angle to the pressure plate
diaphragm spring
created from flat spring steel in a dish shape
what are the clutch driven members
the clutch discs and transmission inputshaft
what are the clutch drive members
the flywheel and the clutch cover/pressure plate assembly also if equipped the intermediate plate is a drive member
name the drive / driven members pressure plate = clutch disc = intermediate plate = clutch disc = flywheel =
pressure plate = drive clutch disc = driven intermediate plate = drive clutch disc = driven flywheel = drive
two types of clutch discs
ridged clutch discs and dampened clutch discs
rigid clutch discs
solid with some sort of lining either bonded or riveted to both sides of the outer diameter - often riveted to central splined hub that slides on the transmission input shaft splines - used where limited amount of engagement and disengagement occur
dampened clutch discs
may be some what flexible - the central splined hub may be attached to the disc through a spring loaded limited movement mechanism design to absorb torsional shock loads
what type of clutch disc design will extend service life of clutches that are disengaged and engaged very frequently
dampened clutch disc type
what are the types of disc lining construction
organic and ceramic
organic disc lining
also called NOA ( non-asbestos organic ) made from various binders, resins and fillers . metallic particles may be added to improve service life where high heat is encountered
ceramic disc lining
used when high heat and heavy loads are encountered . provide very good resistance to slippage during the engagement process
intermediate plates
are used when two clutch discs are used
why must the intermediate plate not be fastened tightly to the flywheel or clutch cover
because one or both of the clutch discs will remain in contact when disengaged
what can be used to reduce noise in the intermediate plate
anti-rattle springs between the drive pins and intermediate plate drive slots or between the drive lugs and drive slots
clutch release levers are used to
move the pressure plate closer to the clutch cover during the disengagement process
release bearing and bearing sleeve assembly
are used to move the clutch release levers
on a push type the release bearing and sleeve will be
rotating all the time the engine is running but will only be under load when the clutch is disengaged and engaged
on a pull type the release bearing and sleeve will be
only rotating when disengaged and engaged
how do manual clutches adjust
push type have a threaded pushrod that moves the release bearing yoke shaft - pull type clutches have an internal threaded ring that must be first unlocked from the clutch cover and then turn to adjust
how do self adjusting clutches self adjust
every time the clutch is disengaged and engaged the self adjusting mechanisim will try to adjust only when it is worn will it self adjust
what is the purpose of clutch breaks
to stop rotation of the clutch disc and transmission input shaft to prevent gear teeth clash when shifting from neutral to first or reverse
clutch brakes that are constructed as a one piece assembly are often called
torque limiting clutch brakes
torque limiting clutch brakes are designed to
slip above a pre determined torque load
why will depressing the clutch pedal to the floor every time a gear selection is made cause premature failure
over works the clutch brake and can cause early failure
what type of brake assembly eliminates the need to remove the transmission for service
a two piece clutch brake assembly
what is one cause of slippage in a clutch
oil spray from leaking seals
if clutch slippage is extreme or occurs often
heat build up is excessive
what will heat build up cause on the clutch springs
loss of spring tension causing less clamping force and more slippage
what causes a dragging clutch
when it is not quickly freed from the flywheel or pressure plate
what damage will a dragging clutch cause
gear clash and gear tooth damage as well as difficulty shifting
what can cause clutch drag
improper adjustment ( excessive free play )
what would happen if the free play was to little
the release bearing and levers could be in constant contact and cause premature failure
what would excessive free play cause
the operator to move the clutch pedal much further before release and causing drag
what must also be kept in mind when checking clutch pedal free play
wear in the connecting linkage
when checking for a dragging clutch what should be kept in mind
flywheel, intermediate plate and the pressure plate may be in contact due to warpage from excessive heat
what would cause chattering in a clutch
loose engine mounts or drivetrain components may be worn or damaged - clutch splines may also be worn
how would oil contamination or grease contamination cause chattering clutch
the disc surface would become glazed and worn creating and unusual wear pattern
what might cause clutch vibration
an imbalance in the clutch assembly -linings could separate and individual sections could be torn off the disc . also dirt or mud build up
prior to removing a clutch from a vehicle you should
disconnect the battery ground cable to prevent engine turnover
when removing the clutch assembly from the engine what should be installed to help you slowly and evenly slide the clutch away
two long guide studs in the clutch cover pressure plate assembly mounting fastener holes
why should you remove the clutch cover in the manufacture pattern
to prevent warpage of the assembly
what should be remembered when removing clutch material
the clutch dust may contain asbestos so breathing protection should be considered
what would you use to check for warpage on the intermediate plate and pressure plate
straight edge and a feeler gauge
when checking the springs you should check for
all the springs are the same height and use a spring gauge to make sure tension is within speck
when cleaning or handling clutch components you should make sure
no oil or grease gets onto the clutch friction surface . clean all parts with steam or water or a brake cleaning solution
after reassembly what should be checked
crankshaft end play
how can the alignment of the re assembled components be checked
with a flywheel runout check
why are crankshaft, flywheel and clutch bore housing checks conducted
to ensure the centerlines of the crankshaft and transmission input shaft are in line with each other
when is the centrifugal clutch in the locked state
at full load speed
what are the common connections when a centrifugal clutch is used
belt - close coupled - flex couples
