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LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2) LV27 manual transmissions systems (2)
kap all phase & 6/11/03 11:36 am Page 23 Student Workbook LV27 Manual Transmission Systems (2) LV27/SWB Student Workbook for Technical Certificates in Light Vehicle Maintenance and Repair MODULE LV27 MANUAL TRANSMISSION SYSTEMS (2) Contents Page Introduction Routine Maintenance: Clutch pedal height – hydraulic Clutch push rod free play – hydraulic Clutch release fork free play – hydraulic Clutch free play – cable Clutch trouble shooting 4 Transmission Routine Maintenance: Gearbox troubleshooting Synchroniser ring wear Shift key and spring wear Gearbox troubleshooting 10 10 11 12 6 Page Gear Shifting: Control mechanisms wear Gearbox troubleshooting Incorrect gear thrust clearance Shift detent wear Gear and shift hub sleeve spline wear Abnormal transmission noise -1Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue 13 13 13 14 14 15 16 -2Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Introduction On completion of this module you will be expected to effectively: • • • • explain the routine maintenance requirements for manual gearboxes explain the routine maintenance requirements for clutches identify common faults with clutch operation identify common faults with manual gearbox operation Routine Maintenance Clutches are designed to require minimal routine maintenance However the following can be carried out during regular scheduled servicing: • • • • • • check clutch operating mechanism (cable or levers) for correct adjustment lubricate, where required, exposed cable and lever joints check degree of clutch disc (or plate), wear can often be judged by the position and feel of the pedal check clutch pedal height and free play check hydraulic clutch fluid level check hydraulic clutch fluid for contamination In this example the clutch master cylinder shares a reservoir with the brake system A baffle inside the reservoir creates two chambers to keep the circuits separate The fluid used in the clutch system is usually identical to that normally used in the brake system It should be changed and the system bled periodically as indicated by the manufacturer or when contamination of the fluid is present -3Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Care should be taken to ensure all air is removed from the circuit by thorough bleeding Routine maintenance is limited to inspection of the system to identify fluid leaks, visual damage or wear and maintaining fluid level Clutch pedal height – hydraulic Clutch pedal height is adjusted by slackening the lock nut and turning the stop bolt in the appropriate direction before securing the lock nut again It is measured as indicated and compared with the manufacturers’ specification If no specification is available it is usually set to match the brake pedal Pedal play must be checked and adjusted if necessary after pedal height adjustment Clutch push rod free play – hydraulic Gently pushing the pedal will establish clutch pedal free play It can be adjusted by slackening the lock nut and turning the push rod in the appropriate direction Pushing the pedal harder will establish total pedal free play Total pedal play is push rod free play plus release fork free play -4Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Clutch release fork free play – hydraulic Release fork free play can be adjusted to specification by slackening the lock nut and turning the push rod in the appropriate direction Clutch pedal height – cable The cable operated system pedal height can be adjusted in the same way as the hydraulic clutch -5Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Clutch free play – cable The cable operated clutch pedal free play is measured in the same manner as the hydraulic system The cable-operated clutch often incorporates a selfadjusting mechanism Release fork free play can be adjusted on some models This usually requires the E-ring or clip to be removed from the cable as indicated Clutch troubleshooting -6Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Clutch disengagement operation can be investigated in the following way: • • • • • • apply hand brake and chock the wheels depress clutch pedal and start the engine release clutch pedal with transmission in neutral without depressing the clutch, very carefully and slowly move the gear stick towards the reverse position as soon as the gears contact fully depress the clutch pedal if reverse gear then selects smoothly you can conclude that the clutch is disengaging correctly A clutch disc or plate slipping under load between the flywheel and pressure plate will soon lead to total clutch failure If the vehicle does not accelerate on a hill climb, despite heavy throttle use, and is accompanied by a strong burning smell the following procedure will determine clutch condition: • apply hand brake and chock the wheels • depress clutch pedal and start the engine • select top gear • gradually increase engine rpm and attempt to drive off • if the engine stalls you can assume the clutch is not slipping -7Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue A clutch grabbing or juddering prevents the vehicle from starting off smoothly The symptoms can usually be exaggerated, for the purpose of diagnosis, by starting off on a hill or with the handbrake partially applied Clutch judder can also be caused by incompatible materials or an overheated and damaged clutch Overheating can increase pressure plate or flywheel run out -8Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Transmission Routine Maintenance Modern transmission systems are designed to require very little routine maintenance Visual inspection of the casing for fluid leaks or damage and the inspection of gear linkage is generally all that is required Few manufacturers specify transmission oil change as part of the periodic servicing of the vehicle Nevertheless, when it is carried out it is vital that the correct oil is used Manufacturers specify oils of very different types for use in manual transmission/transaxle These vary from standard API class transmissions oils to Dexron automatic fluids Oil drained from the plug indicated, should be checked for particles of the internal components of the gearbox This can give an indication of wear taking place within the transmission The oil filler plug often doubles as the level indicator to help prevent over filling Care should be taken not to remove the securing bolts indicated, by mistake This error often requires the transmission to be rebuilt to relocate items within -9Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Gearbox troubleshooting Synchroniser ring wear Grooves are provided on the inner surface of the synchroniser ring They have the effect of cutting through the oil film to increase friction between the ring and the cone If the grooves become worn, friction can be lost This will lead to poor synchronisation of the mashing gear speeds and gear crunching during selection -10Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Synchroniser ring wear can be assessed by checking the clearance when fitted onto the gear Attempting to turn the ring on the gear by hand will also give an indication of excessive wear Shift key and spring wear The shifting keys are kept under tension by the shift key spring If the spring becomes weak the key will not force the synchroniser ring against the gear correctly The projecting part of the key may be worn excessively Both problems can be the cause of gear crunching -11Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Gearbox troubleshooting -12Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Gear Shifting Control mechanisms wear Remote gear selection mechanisms can be a source of stiffness and wear Floor mounted mechanisms have cables or rods that can be exposed to road dirt and damage Cables may become worn or stiff Gearbox troubleshooting -13Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Incorrect gear thrust clearance Incorrect gear thrust clearance due to wear or damage can mean that the gears no longer mesh accurately This can cause the transmission to jump out of gear In this illustration thrust clearance is being measured on a partially dissembled shaft Shift detent wear The fork shafts have grooves into which detent balls are forced by the springs This prevents the transmission from jumping out of gear and provides a positive feedback to the driver If the springs become weak the transmission will jump out of gear more easily -14Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Gear and shift hub sleeve spline wear The hub sleeve splines have been chamfered on this reverse gear mechanism A corresponding taper on the gear spline helps prevent the transmission from jumping out of gear The transmission will jump out of gear more easily if the splines become worn -15Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Abnormal transmission noise Abnormal noise or selection crunching that affects all gears is often a fault with the clutch Crunching or noise that affects only one gear is most likely to be a fault within the transmission gearbox Therefore it is important to check the operation of the clutch prior to carrying out investigation of the gearbox If depressing the clutch pedal with the engine running in neutral stops an abnormal noise it is most likely to originate in the gearbox However abnormal transmission noise often only occurs when the vehicle is moving and the transmission is under load A suitable road test is then required to attempt to locate the problem -16Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue ... Rights Reserved LV27: Manual Transmission Systems (2) Issue 13 13 13 14 14 15 16 -2Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Introduction... Rights Reserved LV27: Manual Transmission Systems (2) Issue Gearbox troubleshooting -12Copyright © Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Gear... Automotive Skills Limited 2003 All Rights Reserved LV27: Manual Transmission Systems (2) Issue Transmission Routine Maintenance Modern transmission systems are designed to require very little routine