CCAS 3381 AUTOMOTIVE SKILL I

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CCAS 3381 AUTOMOTIVE SKILL I

• TRANSMISSION

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OBJECTIVES

• To understand the operational principles and
  basic mechanisms of transmission system

Lecture 1 hour Workshop 1 hour
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TRANSMISSION SYSTEM (1)
Manual gear box
Manual gear knob
Manual transmission system
Manual gear box
5-speed manual gearbox
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TRANSMISSION SYSTEM (2)

• Green shaft (input shaft) gear turn at the same
  rpm as the engine
• Red shaft (layshaft) gears are directly
  connected to the input so it spins when input
  shaft spins
• Yellow shaft (output shaft) is splined shaft
  connected directly to drive shaft through
  differential to drive wheels (If wheels are
  spinning output shaft spins)
• If engine is off with car coasting output shaft
  turns inside blue gears (blue gears layshaft
  are motionless)
• Collar connects one of two blue gears to output
  shaft via dog teeth

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TRANSMISSION SYSTEM (3)

• Moving knob forward backward moves collar to
  engage the gears
• Reverse gear is handled by a small idler gear
  (purple)
• Importance of transmission
• Engine redline (max. rpm above which engine
  explodes)
• Engines have narrow rpm ranges (horsepower
  torque are at their maximum)
• Synchronizers allow collar gear to make
  frictional contact before dog teeth make contact
  (collar gear synchronize their speeds before
  teeth need to engage

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TRANSMISSION SYSTEM (4)

• A car engine spins all the time car wheels
  don't (to stop without killing the engine wheels,
  engine needs to be disconnected from the engine)
• Flywheel connected to engine
• Clutch plate connected to the transmission

Spring
Pressure plate
Spring
Clutch plate
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TRANSMISSION SYSTEM (5)

• Springs force on pressure plate
• Clutch plate springs - isolate transmission from
  shock of clutch engaging
• Friction material on the clutch disc wears out
  (similar to the friction material on the pads of
  a disc brake pads/shoes of a drum brake clutch
  slips lost of power)
• Driver who slips the clutch a lot will wear out
  clutch a lot faster
• Worn throw-out bearing (rumbling noise whenever
  the clutch engages)

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TRANSMISSION SYSTEM (6)

• Other clutches
• Automatic transmission with several clutches used
  to engage and disengage various sets of planetary
  gears
• Car air conditioning compressor with magnetic
  clutch
• Engine-driven cooling fan with thermostatically
  controlled viscous clutch

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TRANSMISSION SYSTEM (7)

• Ideally, transmission should be flexible in its
  ratios that engine runs at its single, best rpm
  value (continuously variable transmission - CVT)
  Honda City

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TRANSMISSION SYSTEM (8)

• Manual transmission checklist
• Check for oil leaks (RM5000 new Kancil gearbox)
• Manual transmission test drive
• With transmission lever in neutral, parking brake
  applied engine idling, listen to any loud
  noises when clutch pedal pressed or released
• Try to drive the car at all speeds one by one -
  every speed should shift smooth easily without
  any noises or jerks

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TRANSMISSION SYSTEM (9)

• Manual transmission test drive
• While driving at 2nd or 3rd gear, try to press
  down sharply on the accelerator pedal for an
  instance (clutch should not slip, any slipping
  i.e., engine rpm increases but speed remains the
  same clutch most likely has to be replaced)
• Try to drive with acceleration deceleration
  (there should be no whining or humming noise
  under any condition with all gears should shift
  easily noiselessly)

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TRANSMISSION SYSTEM (10)

• Automatic transmissions
• no clutch pedal
• no gear shift
• Automatic transmission (gearbox plus torque
  converter) like manual gearbox its clutch

Torque converter
Auto gearbox
Auto transmission system
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TRANSMISSION SYSTEM (11)

• In automatic transmission, same set of gears
  produces all of the different gear ratios
  (planetary gearset)
• Planetary gearset
• A set of bands to lock parts of gearset
• Three wet-plate clutches to lock other parts of
  gearset
• Hydraulic system controlling clutches bands
• Large gear pump to move transmission fluid around
  
• Planetary gearset has 3 main parts
• Sun gear
• Planet gears planet gears' carrier
• Ring gear

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TRANSMISSION SYSTEM (12)
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TRANSMISSION SYSTEM (13)

• Each of these 3 parts can be input, output or
  stationary (determines gear ratio)
• First Gear - 2.41
• Second Gear - 0.671
• 3rd gear - 11 ratio in 3rd gear
• Overdrive has a faster output speed than input
  speed (output of engine goes straight to
  transmission)
• Ratio 1 / (1 S/R) 1 / ( 1 36/72) 0.671
  (an engine turning at 2000 rev/min output speed
  is 3000 RPM allowing cars to drive at freeway
  speed while the engine speed stays nice and slow

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TRANSMISSION SYSTEM (14)

• Differentials (where engine power, in most cars,
  makes its last stop before spinning the wheels)
• Aim engine power at the wheels
• Act as final gear reduction in the car (reduce
  rotational speed of transmission one final time
  before it hits the wheels)
• Transmit power to the wheels while allowing them
  to rotate at different speeds during turning
• Device that splits engine torque two ways,
  allowing each output to spin at a different speed
• Differential is found on all modern cars
  trucks, and also in many all-wheel-drive
  (full-time 4WD vehicles)

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TRANSMISSION SYSTEM (15)
Differential
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TRANSMISSION SYSTEM (16)

• Final drive ratio (gear ratio in the
  differential)
• Open differential always applies the same amount
  of torque to each wheel
• Two factors determining how much torque can be
  applied to the wheels
• equipment
• traction

• Dry conditions - torque applied to wheels limited
  by engine gearing

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TRANSMISSION SYSTEM (17)

• In low traction - amount of torque limited to
  greatest amount that will not cause a wheel to
  slip under those conditions (if you give the car
  more gas after the wheels start to slip, the
  wheels will just spin faster problem with open
  differentials
• Limited slip differential (LSD) positraction -
  allows more torque to be transferred to the
  non-slipping wheel

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TRANSMISSION SYSTEM (18)

• Automatic transmission checklist
• Place your car at a level surface, start engine,
  set transmission lever to "P let engine idle
• Pull transmission dipstick
• Wipe it off with a lint free clean rag/tissue
• Insert it back carefully all the way down into
  its place
• Pull again check fluid level

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TRANSMISSION SYSTEM (19)

• Automatic transmission checklist
• Pull again check fluid level
• Engine cold fluid within "COLD" marks
• Engine hot fluid level at upper end of "HOT" mark
  (top it up if it is lower)
• Check fluid condition also too black a burnt
  smell -transmission may not last

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TRANSMISSION SYSTEM (20)

• Automatic transmission checklist
• Pull again check fluid level
• There should not be any metal filings or black
  flakes
• Topping up transmission fluid
• Use only specified transmission fluid (check your
  manual)

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TRANSMISSION SYSTEM (21)

• Topping up transmission fluid
• Add a small amount of fluid through dipstick pipe
  as shown in the image do not overfill it
• Wait for a few minutes to let fluid to flow down
• Start engine check level again

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TRANSMISSION SYSTEM (22)

• Transmission maintenance
• Most of transmission troubles start after
  overheating
• Under heavy load
• Continuous stop go traffic in hot weather
• Racing
• Accelerating too hard to free the car
• At higher temperatures transmission fluid burns
  loosing its lubricating qualities becomes
  oxidized leaving deposits all over inside
• Exposed to heat rubber seals gaskets inside
  transmission become hardened causing leaks

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TRANSMISSION SYSTEM (23)

• Transmission maintenance
• Most of transmission troubles start after
  overheating
• Metal parts warp loose their strength
• Poor design
• After being rebuilt by inexperienced technician
• Harsh driving
• Too low or too high transmission fluid level
• Wrong transmission fluid type

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TRANSMISSION SYSTEM (24)

• How to prevent the transmission from damage
• Always check your parking space for leaks (get it
  fixed before it caused something serious)
• Once in a while check transmission fluid level
  condition
• Use only same type of the transmission fluid as
  specified in owner's manual
• Never shift to R or P until car comes to a
  complete stop

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TRANSMISSION SYSTEM (24)

• How to prevent the transmission from damage
• Never shift from P mode when engine rpm is
  higher than normal idle
• Always hold a brake down when shifting from P
• Do not tow with drive wheels on the road
• Go to transmission shop when you experience any
  problems with your transmission such as leaks,
  noises, problems with shifting, etc.

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TRANSMISSION SYSTEM (25)

• ATF (owners manual)
• Fluid change (40,000 km or so)
• Good conditions clean odorless
• Transmission screen/filter

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THE END
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