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Today's Lesson - Words to Know When Working on a Car

 
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Old 07-23-2008, 05:22 PM
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Icon1 Today's Lesson - Words to Know When Working on a Car

For those of you who don't already know, my name is Rhys, and I am here to better myself as a Student and to become somewhat of a "teacher". I will be posting notes on this thread for all to read and see, and then there will be a thread in the Off Topic section where we can have discussions about the notes, and you can ask questions, basically do whatever.

*EDIT* - ALL INFORMATION TAKEN FROM: Manual Transmissions and Transaxles: 4th edition Classroom Manual BY Jack Erjavek

Here goes nothing

Here is the first one, did it last night...

Drive train – 4 Primary purposes
1. Connect and disconnect the engines power to the wheels.
2. Select different speed ratios.
3. Provide a way to move the car in reverse.
4. Control power to the drive wheels for safe turning .
Main Components – all depending on whether the vehicle is FWD, RWD or AWD
- Clutch
- Transmission
- Differential
- Drive Axles
FWD – Front Wheel Drive
- Power goes from the clutch to the torque converter to the transmission, then to the front differential, then to the driving axles and then the front wheels.
- The transmission and differential are housed in a single unit called a transaxle.
- Gear sets in the transaxle provide required gear ratios and direct the power flow into the differential. The differential gearing provides the final gear reduction and splits the power between the left and right axles.
Drive Axles
- Extend from the sides of the transaxle and are fitted to the hubs of the drive wheels.
- Constant Velocity (CV) joints mounted to each end of the drive axles allow for change in length and angle without affecting power flow to the wheels.
RWD – Rear Wheel Drive
- Most pickups, minivans and SUV’s are RWD, along with some luxury and performance cars.
- Power flows from the clutch to the manual or auto transmission, then to the driveline (drive shaft assembly). From there it goes thru the rear differential, the rear drive axles and then the rear wheels.
AWD/4WD – All Wheel Drive/4Wheel Drive
- Combines the features of both FWD and RWD so power can be delivered to all wheels all the time, or when the condition or driver selects 2 wheel or 4 wheel drive.
- Normally a 4WD pickup or full size SUV has a modified RWD set up to include the front axles, whereas a smaller SUV or car has a modified FWD set up to include the rear axles.
- 2 sets of gears in the drive train: Transmission and Differential.
- Transmission: allows the gear ratios to change.
- Differential Unit: changes the power output from the transmission and allows the drive wheels to rotate at different speeds during turns, which prevents tire scuffing.
- Thru the use of different gear ratios, torque is multiplied.
Transmission
- Mounted to the rear of the engine and designed to allow the car to move forward and reverse. Also has a neutral position which allows the engine to run without applying power to the drive wheels. This means there is input to the transmission but no output because the driving gears are not engaged.
- Automatic – combination of a torque converter and planetary gear system to change gear ratios automatically.
- Manual – assembly of gears and shafts that transmit power from the engine to the drive axles. Changes in gear ratios are controlled by the driver.
Torque X RPM = HP
5252
Gear Ratios
- High Number + High Torque + Low Max Speed = Low Gear.
- Low Number + Low Torque + High Max Speed = High Gear.
- 4:1 gear ratio is lower than 2:1 ratio.
- Ratio of teeth on driven gear to the teeth on the drive gear.
Manual
- By moving the shift lever when the clutch is disengaged, various gear and speed ratios can be selected. The gears are selected to give the driver a choice of speed and torque.
- Low gears provide low max speed but high torque
- High gears provide high max speed but low torque.
- Have either 4, 5 or 6 forward speeds.
- Different gear ratios are needed because an engine develops little power at low engine speeds. It must be turning at fairly high speeds before it can deliver enough power to move the car. Thru the selection of proper gear ratios, torque applied to the drive wheels can be multiplied.
- Manual transmissions are Constant Mesh, Fully Synchronized transmission
- Constant Mesh: Transmission gears are constantly in mesh with each other regardless of whether the car is stationary or moving.
- Fully Synchronized: mechanism of brass rings and synchronizers used to bring the rotating shafts and gears of the transmission to 1 speed for smooth up and down shifting.
CVT – Continuously Variable Transmission
- Transmission without fixed forward speeds. Gear ratios vary with engine speed and load.
- These automatic like transaxles do not have a torque converter. They have a manual type flywheel with a start clutch, instead of relying on gear sets to provide drive ratios it uses belts and pulleys.
- One pulley is the driven member and the other is the driver. Each pulley has a moveable face and a fixed face. When the moveable face moves, the effective diameter of the pulley changes. The change in effective diameter changes the effective pulley (gear) ratio. A steel belt links the driven and drive pulleys together.
- To achieve low pulley ratios: High hydraulic pressure works on the moveable face of the driven pulley to make it larger. In response to this high pressure, the pressure on the drive pulley is reduced. Because the belt links the two pulleys and proper belt tension is critical, the drive pulley reduces just to keep the proper belt tension on the belt. The increase of pressure at the driven pulley is proportional to the decrease of pressure at the drive pulley.
- The opposite is true for high pulley ratios: low pressure causes the driven pulley to decrease in size whereas high pressure increases the size of drive pulley.
- Vehicle loads and speeds can be changed without changing the ENGINE SPEED, because the size and drive pulleys can vary so greatly. Engine operating at most efficient speed = better fuel economy and less emissions.
Flywheel
- Large and heavy disc that is attached to the rear end of the crankshaft.
- Rear face is machined flat and smooth to serve as the driving member of the clutch. When the clutch is engaged, the rotary motion of the crankshaft is transferred from the flywheel, thru the clutch, to the transmission. The rotary motion is then delivered to by the transmission to the differential, then it’s transferred by the axle shafts to the wheels.
- Acts as a balancer for the engine and it smoothens out and dampens engine vibrations caused by firing pulses.
Clutch Assembly
- Immediately to the rear of the engine and is directly connected to the crankshaft at the flywheel. Its purpose is to engage and disengage the engines power smoothly to the rest of the drive train.
- When the driver depresses the clutch pedal it disengages the clutch and the engine is disconnected from the drive train. This allows the engine to run while the car is standing still. The clutch is engaged when the clutch pedal is off the floor and the engine is connected to the drive train.
- 2 disc system: Flywheel serves as one disc and the pressure plate is the other. A third disc, the clutch disc, is squeezed between the two and thru friction, it connects them. If they aren’t connected, one wheel spins freely while the other stands still, until they are pushed together, then they spin as one.
Clutch Disc
- Made of high friction material that provides for a solid connection between the flywheel and clutch assembly.
- The discs are forced together by strong springs, which clamp the discs together.
- Spring pressure is released by pushing down on the clutch pedal, which allows the discs to separate and the driver to shift gears.
- some performance clutch assemblies use multiple clutch discs which are separated by intermediate plates.

Components: Flywheel, Clutch Disc, Pressure Plate Assembly, Clutch Fork, Release Bearing and Hub, Clutch Housing, Clutch Fork Ball Stud, Input Shaft

Pilot Bearing
- The clutch shaft projects from the front of the transmission. Most of them have a smaller shaft or pilot shaft that projects from the outer end.
- This pilot rides in the pilot bearing in the crankshaft’s flange or flywheel.
- The pilot bearing (or bushing) serves as a support for the outer end of the input. shaft and maintains alignment of the shafts with the crankshaft.
- These are normally pressed into the bore of the crankshaft.
Release Bearing
- Ball type bearing located in the bell housing and operated by the clutch linkage
- Usually sealed and pre-lubricated to provide smooth and quite operation as they move against the pressure plate to disengage the clutch, often called a “throw out bearing”.
- Mounted on an iron casting called a Hub, which slides on a hollow shaft at the front of the transmission housing, the hollow shaft is a part of the transmissions front bearing retainer.
Cable Type Clutch Linkage
- Simple and lightweight, it connects the pivot of the clutch pedal directly to the release fork
- Compact and flexible and eliminates wearing of pivot points of a shaft and lever linkage. However cables will gradually stretch and break due to electrolysis.
- Typically the cable is connected to the pedal assembly. At the pedal assembly there is a spring that keeps the pedal in the up position, and the cable is held under tension by the release fork.
- This end is fitted with an adjusting nut and lock nut that allows for pedal free play adjustments.
Hydraulic Linkage
- Consists of master cylinder, hydraulic tubing and slave cylinder
- Master cylinder is attached to and activated by the clutch pedal thru an actuator rod.
- The slave cylinder is attached to the master cylinder by flexible pressure hose or metal tubing and is positioned so that it can work directly on the clutch release yoke lever.
- Depressing the clutch pedal forces the actuator rod into the bore of the master cylinder.
- As the pedal pushes farther, fluid is forced from the master cylinder to the slave cylinder. This fluid is under pressure and causes the piston of the slave cylinder to move. This pushes the slave pushrod against the release fork and bearing, thus disengaging the clutch. When the pedal is released, the springs of the pressure plate push the slave cylinders pushrod back, forcing the fluid back into the master cylinder.

the thread for discussions is here: http://www.preludezone.com/showthrea...032#post164032
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Last edited by OEM~KaOs; 07-26-2008 at 05:03 PM.
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Old 07-24-2008, 11:27 PM
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Well, I wanted to post my notes on the CVT transmissions, I find them absolutely fascinating, but I forgot one of the pages at work…so tomorrow morning I will post about the CVT’s

On a side note, the pictures are to see the arrows and the direction and operation of power flow in each gear.

Today’s topic is the Operation and Power flow of a 5 Speed Transmission:

Basic Operation of a Manual Transmission
- All 4, 5 or 6 forward helical gear assemblies are in constant mesh, and are activated by the 1st/2nd, 3rd/4th and the 5th synchronizer.
- Each synchronizer is activated by it’s own shift fork, and all three forks slide along the transmissions single shifter rail
- The reverse idler gear slides along another rail to engage reverse gear
- With all the gears in constant mesh, all the gears rotate when the input shaft is applying power BUT the gears will NOT transfer power to the main shaft until one of the synchronizers engages a gear
- If the gear(s) are not engaged by a synchronizer they are free wheeling on the main shaft
- The individual output shaft gears are mechanically locked to the output shaft ONLY when the synchronizers are activated, all other times they rotate independently of the output shaft
Power Flow in Neutral
- Input shaft drives the countershaft gears but NO power is transferred out of the transmission
- The gears all spin freely because no synchronizer is engaged

Power Flow in First
- Power enters the transmission thru the input shaft and rotates the countershaft gear
- The 1st/2nd synchronizer sleeve is engaged with the dog teeth on the 1st speed gear, locking into the main shaft
- Power coming in the input shaft transfers thru the counter gear and up into the 1st gear
- This gear rotates the synchronizer sleeve, which rotates the main hub and output shaft for power
- All other gears are spinning freely on the main shaft

Power Flow in Second
- Input shaft drives the counter shaft gear
- 1st/2nd synchronizer sleeve is moved to engage the dog teeth of 2nd gear, locking it to the output shaft
- Power comes into the input shaft, down the counter gear and up to the 2nd gear
- Dog teeth of 2nd gear rotates synchronizer sleeve, which rotates the main hub and main shaft for output power

Power Flow in Third
- This gear causes the counter shaft gear, which is driven by the input shaft, to mechanically lock to the 3rd gear output shaft
- The 3rd/4th synchronizer sleeve is moved to engage with the dog teeth of 3rd gear
- Power comes from the input shaft to the counter gear and then to the 3rd gear
- The dog teeth on the 3rd gear rotates the synchronizer sleeve which rotates the hub and main shaft for output power

Power Flow in Fourth
- Mechanically locks the output shaft to the input shaft
- 3rd/4th synchronizer sleeve is moved to engage dog teeth of the INPUT GEAR
- Power flows in from the input shaft, thru the synchronizer sleeve and main hub and then thru the main shaft for output power
- This directly links the two shafts and then the output shaft rotates at the same speed as the input shaft and provides “Direct Drive”

Power Flow in Fifth (Overdrive)
- Causes counter shaft gear, which is driven by the input shaft, to rotate the 5th gear
- 5th gear synchronizer sleeve is moved to engage the dog teeth on the 5th gear
- Power on input gear is transferred to the counter gear and then to the 5th gear
- Power transfers thru the synchronizer sleeve and hub to the main shaft power
- This results in the output shaft rotating FASTER then the input shaft

Power Flow in Reverse
- If the transmission has a reverse synchronizer gear, the reverse synchronizer sleeve moves to engage with the reverse gear
- Power comes in thru the input shaft, into the counter gear, thru the reverse idler gear and into the reverse gear on the main shaft
- Reverse gear rotates the synchronizer sleeve, which rotates the hub and main shaft in a reverse direction
- For a NON SYNCHRONIZED transmission, a reverse gear shift relay slides the reverse idler gear into contact with the counter shaft reverse gear and then the reverse gear onto the output shaft
- Reverse idler gear causes the reverse output shaft gear to rotate COUNTERCLOCKWISE
- Counter shaft rotates counterclockwise and causes the output shaft to rotate CLOCKWISE to produce forward motion of the vehicle, but in REVERSE


That’s all for today’s lesson, tomorrow you can look forward to learning about CVT Transmissions!!

Thanks for reading, hope to hear your input, discussions and questions!!
the thread for discussions is here: http://www.preludezone.com/showthrea...032#post164032
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Old 07-26-2008, 05:01 PM
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Alright Ladies and Gentleman - the CVT transmission post is UP!!

Enjoy:

CVT – Continuously Variable Transmission
- Unconventional transmission design and considered an automatic transmission because the driver does nothing to the gears, BUT the design is more mechanical then an automatic transmission, there it is sort of a manual transmission
- Basically, it’s a transmission with no fixed forward speeds and the gear ratio varies with engine load and speed, but it does have 1 speed reverse gear
- A CVT automatically selects the best over ratio for all operating conditions continuously, and during drive ratio changes there is NO perceptive shift.
- At maximum acceleration, drive ratio is adjusted for maximum horsepower
- At constant vehicle speed, the drive ratio is adjusted for obtaining maximum fuel mileage and maintaining good drivability
- Each pulley consists of a pair of cones that can be moved closer together or further apart to adjust the diameter at which the belt operates
- Some late model CVT’s are equipped with a feature that simulates a manual shifting transmission. They have 5 or 6 pre-determined areas that the pulleys stop at when the driver selects manual control. These “stops” provide the feel and effect of shifting into distinct gear ratios
- The CVT is controlled electronically
Designs
- Torodial Design:
o Uses a moveable roller between two curved metal plates. One plate is the input and the other is the output
o By changing the angle and position at which the roller touches the plates, the drive ratio is then varied
o Typically used with engines the have high torque output
- Rubber Belt Design
o Uses a rubber belt that transfers power between 2 variable width pulleys
- Steel Push Belt Design
o Uses a steel push belt running 2 variable width pulleys
EXAMPLES
- Honda CVT
o System includes: TCM (Transmission Control Module), various sensors, 3 linear solenoids and an inhibitor solenoid
o Pulley ratios are always controlled by the CONTROL system
o Input from the various sensors determines which linear solenoid the TCM will activate
o Activating the shift control solenoid changes the shift control valve pressure, causing the shift valve to move. This changes the pressures applied to the driven and drive pulleys, which change the effective pulley ratio
o Activating the start clutch control solenoid moves the start clutch valve. This allows or disallows pressure to the start clutch assembly. When pressure is applied to the clutch, power is transmitted from the pulleys to the final drive gear set
o The start clutch allows for smooth starting, and because this transaxle doesn’t have a torque converter, the start clutch is designed to slip just enough to get the car moving with out stalling or straining the engine
o Slippage is controlled by the hydraulic pressure applied to the start clutch
o To compensate for engine loads, the TCM monitors the engines’ vacuum and compares it to the measured volume of the engine when the transaxle was in park or neutral
o TCM controls pulley ratios to reduce engine speed and maintain ideal engine temperatures during acceleration. If it’s continuously at full throttle acceleration, the TCM causes an increase in pulley ratio. This reduces engine speed and maintains normal engine temperature while NOT adversely affecting the acceleration
o After the car has been driven at lower speeds or not accelerated for a while, the TCM lowers the pulley ratio
o When in reverse the TCM sends a signal to the PCM (powertrain control module), which turns off the air conditioning and causes a slight increase in engine speed
- Nissan CVT
o Uses a steel push belt that was developed to enable CVT’s to mate with high output engines
o Made of a series of small plates held in position by a cable
o When torque is applied to the belt as it rotates off the drive pulley, the plates lock together and the belt becomes a solid link, but as it begins to rotate around the driven pulley, torque is no longer applied and it becomes flexible
o To help in the activity of the belt, the CVT’s have a special oil that helps lock the belt to the pulleys and lubricates and cools the transmission
o Controlling the temperature of the fluid is important, so there are 3 transmission coolers
o Has 1 clutch and a simple planetary gear set used for neutral and reverse
o They added a torque converter for smoother operation at slow speeds, but once the vehicle is moving it locks up to allow the belt and pulleys to provide the drive ratios
- Audi Stepless Multitronic CVT
o 2 variable pulleys and a steel belt that uses adjacent rows of plates linked together with cradle type pressure pieces (oval shaped pins). These are jammed between the tapered sides of the pulleys and pressed together. (I see these as being like CHAINSAW CHAINS)
o Torque is transmitted by frictional force between the ends of the contact faces of the pulleys and the ends of the cradle pieces
o 2 wet clutches are used to change from forward to reverse. A planetary gear set is used in conjunction with the clutches to change the direction. The clutches are applied when the shifter is placed into Drive or Reverse

That’s all for today’s lesson, tomorrow you can look forward to learning about Drive Axles!!

Thanks for reading, hope to hear your input, discussions and questions!!
the thread for discussions is here: http://www.preludezone.com/showthrea...032#post164032
__________________

'03 Sonic Yellow WRX with 114,000 miles, '05 WRX transmission with 60,000 miles - 310hp booOOOSST!!!

Member #2 of BB Squad
I Love E-FIGHTING Member #2
I'm SUPER Jealous of Irish Luder's Type-S" Bandwagon Member #1
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