CCAS 3381 AUTOMOTIVE SKILL I TRANSMISSION

OBJECTIVES To understand the operational principles and basic mechanisms of transmission system Lecture – 1 hour Workshop – 1 hour

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

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

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

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

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)

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

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

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

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)

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

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

TRANSMISSION SYSTEM (12)

TRANSMISSION SYSTEM (13) Each of these 3 parts can be input, output or stationary (determines gear ratio) First Gear - 2.4:1 Second Gear - 0.67:1 3rd gear - 1:1 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) = 0.67:1 (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

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)

TRANSMISSION SYSTEM (15) Differential

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

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

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

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

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)

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

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

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

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

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.

TRANSMISSION SYSTEM (25) ATF (owner’s manual) Fluid change (40,000 km or so) Good conditions – clean & odorless Transmission screen/filter

THE END IQ + EQ + SQ = TQ*