AUTOMOTIVE TECHNOLOGY.pdf

7. Construction and Operation

1. Cover
 The cover (also referred to as a front) is the outside half of the housing toward the
engine side from the weld line. The cover serves to attach the converter to the
flywheel (engine) and contains the fluid. While the torque converter cover is not
actively involved in the characteristics of the performance, it is important that the
cover remains rigid under stress (torsional and thrust stress and the tremendous
hydraulic pressure generated by the torque converter internally.)

2. Turbine
 The converter turbine rides within the cover and is attached to the drive train via a
spline fit to the input shaft of the transmission. When the turbine moves, the car
moves.

3. Stator
 The stator can be described as the "brain" of the torque converter, although the stator
is by no means the sole determiner of converter function and characteristics. The
stator, which changes fluid flow between the turbine and pump, is what makes a
torque converter (multiplier) and not strictly a fluid coupler.

4. Impeller
 The impeller pump is the outside half of the converter on the transmission side of the
weld line. Inside the impeller pump is a series of longitudinal fins, which drive the
fluid around its outside diameter into the turbine, since this component is welded to
the cover, which is bolted to the flywheel. The size of the torque converter (and
pump) and the number and shape of the fins all affect the characteristics of the
converter. If long torque converter life is an objective, it is extremely important that
the fins of the impeller pump are adequately reinforced against fatigue and the outside
housing does not distort under stress.

98

5.0.7.5 Stall Speed
 The stall speed is the rpm that a given torque converter (impeller) has to spin in order
to overcome a given amount of load and begin moving the turbine. When referring to
"how much stall will I get from this torque converter", it means how fast (rpm) must
the torque converter spin to generate enough fluid force on the turbine to overcome
the resting inertia of the vehicle at wide open throttle.

 Load originates from two places :

a. From the torque imparted on the torque converter by the engine via the
crankshaft. (This load varies over rpm i.e. torque curve and is directly
affected by atmosphere, fuel and engine conditions.)

b. From inertia, the resistance of the vehicle to acceleration, that places a

load on the torque converter through the drive train.

8. Operation of Automatic Gear Shifting Mechanisms

1. Mod (P)
 This selection mechanically locks the output shaft of transmission, restricting
the vehicle from moving in any direction. A parking pawl prevents the
transmission from rotating, and therefore prevents the vehicle from moving,
although the vehicle's non-driven road wheels may still rotate freely. For this
reason, it is recommended to use the hand brake (or parking brake) because
this actually locks (in most cases) the rear wheels and prevents them from
moving.

2. Mode (R)
 This engages reverse gear within the transmission, giving the ability for the
vehicle to drive backwards. For the driver to select reverse in modern
transmissions, they must come to a complete stop, push the shift lock button in
(or pull the shift lever forward in the case of a column shifter) and select
reverse. Not coming to a complete stop can cause severe damage to the
transmission.

99

3. Neutral/No gear (N)
 This disengages all gear trains within the transmission, effectively
disconnecting the transmission from the driven road wheels, so the vehicle is
able to move freely under its own weight and gain momentum without the
motive force from the engine (engine braking). This is the only other selection
in which the vehicle's engine can be started.

4. Drive (D)
 This position allows the transmission to engage the full range of available
forward gear trains, and therefore allows the vehicle to move forward and
accelerate through its range of gears. The number of gear ratios of a
transmission depends on the model, but they initially ranged from three
(predominant before the 1990s) to four and five speeds (losing popularity to
six-speed autos, though still favoured.

5. Overdrive (D, OD or a boxed [D])
 This mode is used in some transmissions to allow early computer-controlled
transmissions to engage the automatic overdrive. In these transmissions, Drive
(D) locks the automatic overdrive off, but is identical otherwise. OD
(Overdrive) in these cars is engaged under steady speeds or low acceleration at
approximately 35–45 mph (56–72 km/h). Under hard acceleration or below
35–45 mph (56–72 km/h), the transmission will automatically downshift.
Vehicles with this option should be driven in this mode unless circumstances
require a lower gear.

6. First (1 or L [Low])
 This mode locks the transmission in first gear only. In older vehicles, it will
not change to any other gear range. Some vehicles will automatically shift up
out of first gear in this mode if a certain RPM range is reached in order to
prevent engine damage. This, like second, can be used during the winter
season, for towing or for downhill driving to increase the engine braking
effect.

100

9. Understand Vehicle Wiring Circuit Diagram

 On each system circuit diagram, there is a lot information that is given to you through
the use of different symbols, colours, numbers and letters.

 Tracing wiring diagram requires understanding the source of power and ground
supplies including the ability to read colour coding abbreviations for the wires and
components. This, coupled with the knowledge of the function of each component,
will teach you how to trace the path of both power and ground supply. Once you
grasp this, you should be able to read any wiring diagrams.

 Most automotive wiring diagrams depict the power source usually on the top of the
wiring diagram and the ground source at the bottom. The wires connect any
components in between, which uses colour coding. This coding makes xxxtracing
easy when testing different components at the same time. In the older times, wiring
diagrams can be put in fewer pages of a book, which makes tracing very easy.

Nowadays, because of the complex system being used, wiring diagrams are made to
show individual system so they can be analysed separately.

10. Wire Colour

CODE WIRE CODE WIRE
COLOUR COLOUR
B BLACK P PINK
BR R
x BROWN SB RED

GR GREEN SKY
L BLUE
LG GRAY SI SILVER
O
BLUE V VIOLET

LIGHT GREEN W WHITE

ORANGE Y YELLOW

101

5.0.10.1 Wire Colours
 Blue wire – colour blue is presented by letter L to separate it from letter B used to
identify Black.
 Also note that there is no light blue wire designation used in lexus wiring harness if
there is any shade of blue, it is considered as blue (L)
 Component Pigtails – the wire colour in component pigtails (such as on igniter).This
colour in electrical wiring diagram represents vehicle harness up to where it is
connected to the component.
 Silver band on the wire insulation – in some wires, you will find a small silver band.
This band indicates that the wire uses PVC insulation. This insulation is lighter in
weight and thinner than the smaller insulation, making the wire diameter smaller than
it actually is.

5.0.11 Electrical Symbol and Circuit In Vehicle

102

103

5.0.12 Abbreviator Symbols Used for System Name

ABBREVIATION MEANING ABBREVIATION MEANING

SYMBOL SYMBOL

A/C Air EGR Exhaust gas

conditioner recirculation

ABS Anti-skid ETACS Electronic
ACD braking SRS time alarm
AYC system
control
Active system
center
differential Supplemental
restraint
Active yaw system
control

5.0.13 Type of Circuit

 A circuit is a complete path for current when voltage is applied. There are three basic
types of circuit

 -Series

 -Parallel
 -Series-Parallel

All circuits require the same basic components:

a) Power source

104

b) Protection Device
c) Conductors
d) Load
e) Control device
f) Ground
5.0.14 Vehicle Electric Circuit

5.0.15 Wiring harness configuration diagram

105

5.0.16 Wire Harness Inspection
a) Wire chafing or rubbing: If harness is mis-routed, the wire wrap insulation may rub
through, exposing the bare wire for a potential short-circuiting to ground.
b) Harness stretched too tightly: This condition can cause an open circuit problem that
will be difficult to detect. Because of excessive tension, the wire strands break away
from the terminal crimps or break internally. When this happens, the insulation of the
wire will look normal , the wire strands will be open.
c) Abnormal kinks or bends: Sharp bends in the wiring harness, particularly where the
wire is subject to repeated flexing, can cause an internal breaking of the wire strands.

5.0.17 Switches and Relay
 Relays are located in entire vehicle. Relay blocks both large and small are located in
the engine compartment; behind the left or right kick panel or under the dashboard.
Relays are often grouped together with other components like fuses or placed by
themselves.

106

5.0.18 Relay Position Identification
Relay/fuse block cover usually labels location and position of each fuse, relay ,or fuse

element contained within.

5.0.19 Understanding Relays
Relay Application

 Relays are remote control electrical switches that are controlled by another
switch, such as a horn switch or a computer as in a power train control
module. Relay allows a small current flow to the circuit to control a higher
current. Several designs of relays are used today such as 3pin,4 pin,5 pin, 6pin,
single switch or dual switches.

107

5.0.20 Fuses and Fusible links
 Fusible links include mechanical and electrical devices.
 A mechanical fusible link is a device consisting of two strips of metal soldered
together with a fusible alloy that is designed to melt at a specific temperature,
thus allowing the two pieces to separate. Mechanical fusible links are utilized
as the triggering device in fire sprinkler systems and mechanical automatic
door release mechanisms that close fire doors in warehouses, etc. Some high-
security safes also utilize fusible link-based re-lockers as a defence against
torches and heat-producing tools. Mechanical fusible links come in a variety
of designs and different temperature ratings.
 An electrical fusible link is a type of electrical fuse that is constructed simply
with a short piece of wire typically four American wire gauge sizes smaller
than the wire that is being protected. For example, an AWG 16 fusible link
might be used to protect AWG 12 wiring. Electrical fusible links are common
in high-current automotive applications. The wire in an electrical fusible link
is encased in high-temperature fire-resistant insulation to reduce hazards when
the wire melts.

108

5.0.21 Continuity Test
 Every electrical circuit requires a complete circuit to operate. Voltage to the load will
not do any good unless there is also a complete ground path to the battery. The ground
path in the case of all metal-bodied cars is the body itself. In plastic-bodied cars, a
separate ground wire is needed to link the load to the chassis. In either case, a poor
ground connection has the same effect as an open switch. Since the circuit is not
complete, so the current does not flow.

 To check wiring continuity, you need an ohmmeter or a self-powered test light. An
ohmmeter is the better choice because it displays the exact amount of resistance
between any two test points. A test light, on the other hand, will glow when there is
continuity but the intensity of the bulb may vary depending on the amount of
resistance in the circuit. However, it is OK for making quick checks.

 Never use an ohmmeter to check resistance in a live circuit. Make sure that there is no
voltage in the circuit by disconnecting it from its power source, by pulling the fuse or
by testing downstream from the circuit switch or relay. Ohmmeters cannot handle

109

normal battery voltage and if you accidentally complete a circuit through the meter,
you may damage your meter.
 Ohmmeters are great for measuring circuit resistance but you have to be careful while
checking electronic components. An ohmmeter works by applying a small voltage
through its test leads and this voltage can be enough to damage some electronic
components such as the oxygen sensor. Special high impedance 10,000 mega-
ohmmeters should be used for electronics testing.
 Tracing wires is not as easy as it looks because the circuit wire will sometimes change
colour after passing through a connector, switch or relay. Always refer to a wiring
diagram when possible. This way, you will know how the wires are routed and what
colours are used

5.0.22 Finding Electrical Fault
 For a "dead" circuit, the first thing to look for is voltage at the load point. Use your
voltmeter or 12-volt test light to check for voltage. If there is voltage, the problem is
either a bad ground connection or the component itself has failed. Check the ground
connection with your ohmmeter. If the ground connection is good, the fault is inside
the component. If there is no voltage in the "hot" wire to the component, then the
problem is in the wiring. Trace back through the fuse panel (or relay or circuit
breaker) until you find voltage. Now look for an open or short circuit that is
preventing the current from reaching its correct destination.
 Next comes the bad connections. The resistance created by a loose or corroded
connection will cause a voltage drop that can have an adverse effect on circuit
components. An ohmmeter can be used to check non-powered circuit connections for
excess resistance, but a better method is to use a voltmeter to check for a voltage drop
across a connection.

110

CHAPTER 6

111

POWER TRAIN AND DIFFRENTIAL UNIT

6 POWER TRAIN UNITS
 In a motor vehicle, the term power train or power plant refers to the group of

components that generate power and deliver it to the road surface, water or air.
 This includes the engine, transmission, driveshafts, differentials and the final drive

(drive wheels, continuous track like with tanks or Caterpillar tractors, propeller, etc.).
Sometimes "power train" is used to refer simply to the engine and transmission
including the other components only if they are integral part of the transmission. In
a carriage or wagon, running gear designates the wheels and axles in distinction from
the body.
 A motor vehicle's driveline consists of the parts of the power train excluding the
engine and transmission. It is the portion of a vehicle, after the transmission that
changes depending on whether a vehicle is front-wheel, rear-wheel, or four-wheel
drive, or less-common six-wheel or eight-wheel drive.

112

1. Differential
 A differential is a device, usually but not necessarily, employing gears capable of
transmitting torque and rotation through three shafts, almost always used in one of
two ways: in one way, it receives one input and provides two outputs, this is found in
most automobiles, and in another way, it combines two inputs to create an output that
is the sum, difference or average of the inputs.
 In automobiles and other wheeled vehicles, the differential allows each of the driving
roadwheel to rotate at different speeds

A cutaway view of an automotive final drive unit which contains the differential

 Input torque is applied to the ring gear (blue) that turns the entire carrier (blue). The

carrier is connected to both the side gears (red and yellow) only through the planet
gear (green) (visual appearances in the diagram notwithstanding). Torque is
transmitted to the side gears through the planet gear. The planet gear revolves around
the axis of the carrier driving the side gears. If the resistance at both wheels is equal,

113

the planet gear revolves without spinning about its own axis and both wheels turn at
the same rate.

 If the left side gear (red) encounters resistance, the planet gear (green) spins as well as
revolving allowing the left side gear to slow down with an equal speeding up of the
right side gear (yellow).

6.0.2 Limited Slip Differential

 A Limited Slip Differential (LSD) is a type of differential gear arrangement that
allows some difference in angular velocity of the output shafts, but imposes a
mechanical bound on the disparity. In an automobile, such limited slip differentials
are sometimes used in place of a standard differential, where they convey certain
dynamic advantages at the expense of greater complexity.

3. Cone Clutch
 A cone clutch serves the same purpose as a disk or plate clutch. However, instead of
mating two spinning disks, the cone clutch uses two conical surfaces to transmit
torque by friction.
114

 The cone clutch transfers a higher torque than plate or disk clutches of the same size
due to the wedging action and increased surface area. Cone clutches are generally
now used only in low peripheral speed applications although they were once common
in automobiles and other combustion engine transmissions.

 They are usually now confined to very specialist transmissions in racing, rallying or in
extreme off-road vehicles, although they are common in power boats. This is because
the clutch does not have to be pushed in all the way and the gears will be changed
quicker. Small cone clutches are used in synchronizer mechanisms in manual
transmissions.

Schematic drawing of a cone clutch:
1. Cones: female cone (green), male cone(blue)
2. Shaft: male cone is sliding on splines
3. Friction material: usually on female cone, here on male cone
4. Spring: brings the male cone back after using the clutch control
5. Clutch control: separating both cones by pressing
6. Rotating direction: both directions of the axis are possible

115

6.0.4 Torsion

 Torsion (full name Torsen Traction) is a type of differential used in automobiles. It
was invented by American Vernon Gleasman and manufactured by the Gleason
Corporation. Torsen is a contraction of Torque-Sensing. TORSEN and TORSEN
Traction are registered trademarks of JTEKT Torsen North America Inc (formerly
Zexel Corporation, formerly Gleason Power Systems).

Torsion differentials can be used in one or more positions on a motor vehicle
a) Center - used to apportion appropriate torque distribution between front and rear axles
on an all-wheel drive vehicle.
b) Rear - used to apportion appropriate torque distribution between left and right sides in
rear axles. This may be on either a rear-wheel drive or four-wheel drive vehicle.
c) Front - used to apportion appropriate torque distribution between left and right sides
in front axles. This may be on either a front-wheel drive or four-wheel drive vehicle.
d) A four-wheel-drive vehicle, for example, may use either one, two, or three Torsen
differentials.

6.0.5 Drive Shaft

Drive shaft with universal joints at each end and a spline in the centre

116

 A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a
mechanical component for transmitting torque and rotation, usually used to connect
other components of a drive train that cannot be connected directly because of
distance or the need to allow relative movement between them.

 Drive shafts are carriers of torque: they are subject to torsion and shear stress,
equivalent to the difference between the input torque and the load. They must
therefore be strong enough to bear the stress, whilst avoiding too much additional
weight as that would in turn increase their inertia.

 Drive shafts frequently incorporate one or more universal joints or jaw couplings and
sometimes a splined joint or prismatic joint to allow for variations in the alignment
and distance between the driving and driven components.

6.0.6 Universal Joint

 A universal joint, universal coupling, U joint, Cardan joint, Hardy-Spicer joint or
Hooke's joint is a joint or coupling in a rigid rod that allows the rod to 'bend' in any
direction and is commonly used in shafts that transmit rotary motion. It consists of a
pair.

6.0.7 Transfer Box

 A transfer case is a part of a four wheel drive system found in four wheel drive and all

wheel drive vehicles. The transfer case is connected to the transmission and also to
the front and rear axles by means of drive shafts. It is also referred to as a "transfer
gear case", "transfer gear box", "transfer box" or "jockey box"

117

 The transfer case receives power from the transmission and sends it to both the front
and rear axles. This can be done with a set of gears, but the majority of transfer cases
manufactured today is chain driven. On some vehicles, such as four wheel drive
trucks or vehicles intended for off-road use, this feature is controlled by the driver.
The driver can put the transfer case into either "two wheel drive" or "four wheel
drive" mode. This is sometimes accomplished by means of a shifter similar to that in
a manual transmission.

6.0.8 Gear Oil

 Gear oil is motor oil made specifically for transmissions, transfer cases
and differentials in automobiles, trucks and other machinery. It is of a
higher viscosity to better protect the gears and is usually associated with a
strong sulfur smell. The high viscosity ensures transfer of lubricant throughout the
gear train. This is necessary since the devices needing this heavy oil do not have
pumps for transferring the oil with only a portion of the lowermost gears bathed in an
oil sump.

 This heavy oil can create viscous drag leading to inefficiencies in vehicle operation.

Some modern automatic transaxles (integrated transmission and differential) do not
use heavy oil at all but lubricate with the lower viscosity hydraulic fluid, which is
available at pressure within the automatic transmission.
 118

6.0.9 Axle Shaft

 An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle

may be fixed to the wheels rotating with them or fixed to its surroundings, with the
wheels rotating around the axle. In the former case, bearings or bushings are
provided at the mounting points where the axle is supported. In the latter case, a
bearing or bushing sits inside the hole in the wheel to allow the wheel or gear to
rotate around the axle. Sometimes, especially on bicycles, the latter type is referred
to as a spindle.

 On cars and trucks, several senses of the word "axle" co-occur in casual usage,

referring to the shaft itself, its housing or simply any transverse pair of wheels. The
shaft itself rotates with the wheel, being either bolted or splined in fixed relation to it
and is called an "axle" or "axle shaft". However, it is equally true that the housing
around it (typically a casting) is also called an "axle" (or "axle housing"). An even
broader (somewhat figurative) sense of the word refers to every transverse pair of
wheels, whether they are connected to each other or not. Thus, even transverse pairs
of wheels in an independent suspension are usually called "an axle".

119