Gear box

ER. PEEYUSH CHAUHAN
ASSISTANT PROFESSOR
(DEPARTMENT OF MECHANICAL ENGINEERING)
Er. Peeyush ChauhanEr. Peeyush Chauhan

“The gear box which is also known as the transmission system. It
is the second element of the power train in an automobile. It is
used to change the speed and torque of vehicle according to
variety of road and load conditions.”
Main functions of a gear box is as follow:
1.Provide the torque needed to move the vehicle under a
variety of road and load conditions. It does this by
changing the gear ratio between the engine crankshaft and
vehicle drive wheels.
2. Be shifted into reverse so the vehicle can move backward.
3. Be shifted into neutral for starting the engine.

1. Counter shaft:- Counter shaft is a shaft which connects
with the clutch shaft directly. It contains the gear which
connects it to the clutch shaft as well as the main shaft.
It may be run at the engine speed or at lower than
engine speed according to gear ratio.
2. Main shaft:-It is the shaft which runs at the vehicle
speed. It carries power from the counter shaft by use of
gears and according to the gear ratio, it runs at different
speed and torque compares to counter shaft. One end of
this shaft is connects with the universal shaft.

3. Gears:- Gears are used to transmit the power from one shaft
to another. They are most useful component of gear box
because the variation is torque of counter shaft and main
shaft is depends on the gear ratio.
If gear ratio is large than one, the main shaft revolves at
lower speed than the counter shaft and the torque of the
main shaft is higher than the counter shaft. On other hand
if the gear ratio is less than one, than the main shaft
revolves at higher speed than the counter shaft and the
torque of the main shaft is lower than the counter shaft.
A small car gear box contains five speed gear ratio and one
reverse gear .

4. Bearings:- Whenever the rotary motion encounters,
bearings are required to support the revolving part and
reduce the friction. In the gear box both counter and
main shaft are supported by the bearing.

1. Manual transmission
i) Sliding mesh gearbox
ii) Constant mesh gearbox
iii) Synchromesh gearbox
2. Automatic transmission
i) Hydromantic gearbox
ii) Torque converter gearbox
3. Epicyclical gearbox

In this type of transmission different speed ratio or gear
ratio is selected by the driver manually.
Some special skill of driving is required to operate this
type of gear box. This is subdivided into three types.
1. Sliding mesh gearbox
2. Constant mesh gearbox
3. Synchromesh gearbox

Simple in construction, Simplest type of gearbox. In this
gearbox, spur gears are used.
It consist of following parts.
1. Output shaft
2.Low and reverse sliding gear
3. Second sliding gear
4. Clutch
5. Input shaft
6. Clutch gear
7. Counter shaft drive gear
8. Counter shaft
9.Low speed gear

10. Second gear
11. reverse gear
12. Reverse idler gear
13. Gear shift fork

This is one of the famous type used in twenty century. In this
gearbox, all the gears are in constant mesh with each other all
the time. The gears on the main shaft rotates freely without
rotating the main shaft.
Constant mesh gear box consists two dog clutches. These
clutches are provided on the main shaft, one between the
clutch gear and the second gear and the other between the first
gear and reverse gear.
When the left side dog clutch is made to slide left by means of
gearshift lever, it meshes with the clutch gear and the vehicle
runs on top speed.

If this clutch slide right and mesh with second gear, then the
vehicle runs on second gear speed. So in constant mesh gear
box we can change the gear ratio by shifting the dog clutch.
This type of gear box is more popular than sliding mesh
because it creates low noise and less wear of gears.

1. Quicker gearing can be achieved.
2.Only damage occurs on dog clutch teeth not teeth of
gear wheels.
3.Synchronizing devices can be used for smooth
engagement of gears.
4.Once the dog clutches are engaged there is no motion
between their teeth but the power is transmitted through
the sliding action on teeth on one wheel on those of other
when the gear teeth are engaged.
5.To transmit the motion properly, the teeth are suitably
shaped.

One big problem occur in constant mesh gear box is that when
the driver engage the dog clutch, the main shaft and gear to be
meshed running at different speed. So when engage this gear
cause wear and tear of dog clutch. This problem is solved by a
synchromesh gear box. This gear box is same as the constant
mesh gear box except dog clutch is replaced by synchromesh
devices.
Synchromesh gear devices works on the principle that two
gears to be engaged are first brought into frictional contact
which equalizes their speed after which they are engaged
readily and smoothly. The synchromesh looks like as the cone
clutch where the outer surface of cone consist the frictional
surface. This type of gear box is widely used in automobile.

1. Manual Transmission offers a better fuel economy
advantage over their automatic counterparts.
2. Manual transmissions are cheaper than automatic
transmissions and require less maintenance than the
automatic one
3. A person driving a car with manual transmission has
direct control over the car than a person who is driving the
car with automatic transmissions.
4. A car with manual transmission provides an extra
throttle while overtaking since the driver can move to
lower gear for more power. Automatic transmission on the
other hand has a delayed reaction time.

5. A car fitted with manual transmission requires a greater
degree of control and involvement from the driver than a
car with automatic transmissions.

1. Driving a car with manual transmission requires greater
degree of skill and application, an inexperienced driver
could have his hands full while driving as he has to multi
task and concentrate on a lot of things simultaneously.
2. While climbing up a hill, a car with automatic
transmission always scores over the one with manual.
3. In a manual transmission smooth and effective shifting
of gears can only be guaranteed by an experienced driver.

A transmission in which various speeds are obtained
automatically is known as automatic transmission.
In this type of gear box driver merely selects the general
car condition such as forward or reverse. The selection,
timing and engagement of gear for the required gear
speed are accomplished automatically when the accelerator
is pressed or depressed.
Automatic transmission needs no gear change lever and
clutch pedal since clutch and transmission is a combined
unit and works automatically.

1. Traditional Automatic Transmission (TAT)
2. Automated-Manual Transmission (AMT)
3. Continuously Variable Transmission (CVT)
4. Dual-Clutch Transmission (DCT)
5. Direct Shift Gearbox (DSG)
6. Tiptronic Transmission (TT)
7. intelligent Manual Transmission (iMT)

1. Traditional Automatic Transmission (TAT)
It’s known as a torque converter automatic. It’s widely-
used automatic transmission found in almost every car.
This transmission uses a hydraulic fluid coupling or a
torque converter to do the job of changing gears instead
of a clutch. The ECU (engine control unit) is directly
connected to this mechanism to allow smooth and precise
engine control of the vehicle.

2. Automated-Manual Transmission (AMT)
It’s also Know semi-automatic transmission. This type of
automatic transmission uses a regular clutch (Not Clutch
Pedal) and gear configuration, but makes use of sensors,
actuators, processors, and pneumatics to simulate manual
gear use.
These types of vehicles are known for jerky engine
performance at low speeds and hard acceleration, but can
get high fuel mileage over long distances.
Depending on the vehicle manufacturer, the automated
manual transmissions have different commercial names
but, in the end, they are the same in terms of functionality:

 Easytronic (Opel)
 Quickshift, Easy-R (Renault)
 Sensodrive (Citroen)
 Selespeed (Alfa Romeo)

List of cars use AMT-
 Maruti Suzuki Celerio.
 Tata Nexon.
 Toyota Yaris.
 Honda Amaze.
 Maruti Suzuki Vitara Brezza.
 Hyundai Verna.
 Maruti Suzuki Dzire.
 Hyundai Santro.

3. Continuously Variable Transmission (CVT)
It’s using belts or pulleys instead of traditional steel gears,
a continuously variable transmission allows for seamless
gear shifting with various ratios dependent on engine
speed or RPM.
A CVT gearbox has a relatively simple arrangement of
two cone-shaped pulleys with a V-shaped drive belt
connecting them. One pulley is attached to the engine,
while the other is joined to the wheels. When you press the
accelerator, the engine revs and the cone moves according
to the amount of power. The other cone adjusts
accordingly so that the drive belt maintains the same
tension, & car accelerates.

Advantages of CVT-
 Steeples Transmission
 Smooth drive
 Better Fuel Consumption
 Good Adaptability
 Better Emission Control
Disadvantages of CVT
 Limited amount of torque
 Higher cost
 High wear

List of cars use CVT-
 Audi A4 (some 1.8t models)
 Chevrolet Spark 1.4 L
 Honda Activa Scooter 0.109 L
 Honda Amaze 1.2L petrol/1.5L diesel
 Honda Brio (2016-present)
 Honda City 1.5 L
 Honda Civic 1.5 L
 Mercedes-Benz A-Class
 Mercedes-Benz B-Class
 Nissan Micra 1.0 L/1.3 L
 Nissan Murano 3.5 L etc.

4. Dual-Clutch Transmission (DCT)
It’s a combination of an automatic and manual
transmission. Also known as a Twin-clutch transmission
(TCT) or a Double-clutch transmission (DCT). A dual-
clutch transmission has no torque converter. Instead, it
uses two separate shafts with their own clutches for gear
changing, one for odd-numbered gears, and one for even
numbered ones. Shifting to higher and lower gears are
seamless, but they can get noisy and can shift roughly after
wear.
The DCT is a dry transmission that does not need the
driver to change the gearbox fluid ever. It leaves the
clutches dry and wears out its frictional quality eventually.

List of cars use DCT-
 Mercedes-AMG CLA 45.
 Porsche 911 Carrera.
 Audi S3.
 Volkswagen Golf R.
 Nissan GT-R.
 Audi R8.
 Volkswagen Jetta GLI.
 Hyundai Veloster Turbo. etc.

5. Direct Shift Gearbox (DSG)
It’s using a similar setup to a dual-clutch transmission, a
direct shift gearbox (DSG) uses two clutches that
disengage alternately in changing gears. This setup offers
fast shifting and smoother acceleration. Modern systems
also provide fuel efficiency that surpass manual gearboxes.
A DSG system is a wet transmission, so expect decades of
service as long as the fluid is changed regularly.

List of cars use DSG-
 Audi A5
 Audi A6
 Audi A7
 Audi A8 (D4)
 Audi Q2
 Audi Q3
 Bugatti Veyron EB 16.4
 Škoda Octavia
 Škoda Rapid (2012)
 Volkswagen Sharan
 Volkswagen Scirocco etc.

6. Tiptronic Transmission (TT)
It’s usually used in performance or sport oriented vehicles,
and also known as “manumatic”, the tiptronic transmission
was pioneered by Porsche in the ‘90s. It functions similarly
to a manual gearbox. It’s uses a torque converter in place
of a clutch pedal.
There is an option for automatic shifting of gears and an
option for the driver to override the automatic mode for
manual selection of gears. There is a built-in safety feature
that prevents the driver from damaging the gearbox
through over-revving when downshifting. It had been 1st
seen in Porsche 911 (in 1990) then adopted by BMW and
Chrysler.

7. intelligent Manual Transmission (iMT)
Hyundai Motor India has announced India debut of
intelligent Manual Transmission (iMT) on Hyundai
VENUE. The iMT technology is essentially a
revolutionary 2-pedal system that eliminates the need for
drivers to constantly use the clutch pedal as in a
conventional manual transmission.
Hyundai’s iMT technology features a Transmission Gear
Shift (TGS) Lever with Intention Sensor, Hydraulic
Actuator and Transmission Control Unit (TCU). The
system has been designed to offer a seamless drive
experience by incorporating a cohesive logic between the
various components on manual transmissions:

 Transmission Control Unit receives signal from TGS
Lever Intention Sensor, indicating drivers desire to
change gears.
 TCU sends signal to engage Hydraulic Actuator
forming Hydraulic Pressure.
 Hydraulic Pressure is then sent to Concentric Slave
Cylinder (CSC) through Clutch Tube.
 Concentric Slave Cylinder uses this pressure to control
the clutch and pressure plate, thereby engaging and
disengaging the clutch.
 Driver is able to seamlessly shift gears without the need
to mechanically operate clutch pedal.

1. Automatic Transmission have no gear pedal so it’s easy
to drive.
2. In Automatic transmissions driver concentrate more on
speed and road position.
3. Automatic transmission is more reliable than manual
transmission.
4. Automatic transmission is better for hilly areas.
5. Automatic transmission is easy to use in heavy traffic.
6. Less manually restrictive because driver is to keep both
hands firmly on the wheel at all times.

1. It's more expensive to buy than a manual.
2. The transmission has more moving parts, which leads to
greater repair costs.
3. Poor fuel efficiency.
4. Heavy weight in compression manual transmission
vehicle.
Compression b/w MT & AT
pdfMT Vs AT.pdf

The gear shift lever or gear shifter are generally use for
gear shifting purpose.
Types of Gear Shifter
1. Manually Gear Shifter
2. Automatically Gear Shifter
(a) Stick shifter
(b) Joystick/ Monostable shifter
(c) Rotary shifter
(d) Stalk shifter
(e) Push button shifter

1. Manually Gear Shifter – It’s use in manually
transmission Vehicles. Its generally a stick type gear
shifter.
2. Automatically Gear Shifter - It’s use in automatic
transmission Vehicles.
(a) Stick shifter – It’s a regular stick like manual gear box
stick but a little slick. It’s can be slotted to Reverse, Drive
or Neutral gears by moving it in a linear direction or in
gated format. Gated format consists of slots in a zigzag
format that prevents the driver to accidentally move the
gear level, a case most prominent in linear shifters.
Example - Maruti Suzuki Alto K10, Honda Jazz etc.

Manual Stick
Shifter
Stick Shifter

(b) Joystick/ Monostable shifter - A joystick or a
Monostable shifter is a kind of the stick shifter, albeit with
a refined functionality and rich looks. Expensive and
luxury cars like BMW and Audi are famous for providing
the Monostable shifter. Example - BMW 3 Series, Audi
A4 etc.
(c) Rotary shifter- Rotary shifters are not too common,
yet the most fascinating looking form of the gear shifts.
The rotary gearshifts arrival with of Jaguar and Land
Rover cars in the country, which offered a fancy pop-up
kind of swivel wheel that can be rotated to shift a gear. It’s
use forsave the space in the car. Example - Jaguar XE,
Renault Kwid 1.0L AMT.etc.

Rotary ShifterJoystick/ Monostable
Shifter

(d) Stalk shifter- This type of lever is installed below the
wiper/ indicator stalk on the steering column. The gear
shift which remains in its positions and functions just like a
Monostable gear level. Example - Mercedes Benz C-Class,
Mercedes Benz GLA-Class, Fiat Padmini Premiere etc.
(e) Push button shifter- Push button shifters are the most
uncommon type of gear shifters available in the market
today. This automatic shifters found in any car, dating back
as early as 1950s. The design of the gear shifters is simple.
It have individual buttons to select the gear slot in car-
P,R,N,D etc.
Example - Fiat Abarth 595 Competizione, Aston Martin
Vanquish etc.

Stalk Shifter Push Button Shifter

P- Parking
R- Reverse
N- Neutral
D- Drive
L- Low
Drive Gear
D1: Increases torque for difficult terrains like mud or sand.
D2: Aids the car in uphill climbing, such as hilly roads, or provides a
quick engine boost similar to its function on manual transmissions.
D3: Sometimes shown as an OD (overdrive) button instead, D3 revs
the engine for efficient overtaking. The overdrive gear ratio causes
the tires to move faster than the engine spins.
M- Manual
Shifted

This type of gear box uses no sliding dogs or gears to engage
but different gear speeds are obtained by merely tightening
brake bands on gear drum.
It consists of a ring gear annular wheel, sun gear and planet
gears with carrier.
In order to obtain different speeds any one of these units can
be held from rotation by means of brake band. The ring gear
contains teeth on it inner circumference and it surrounded by a
brake band. The brake band is operated by a gear stick or lever
to grip the ring gear and hold its movement.

The sun gear is attached to the clutch shaft thus moves
along with the movement of engine crankshaft.
The planet gears are in constant mesh with both the sun
gear and ring gear and are free to rotate on their axes
carried by the carrier frame which in turn is connected to
the driver shaft.
When the ring gear is locked by the brake band, the
rotating sun gear causes the planet gears to rotate. Since
the ring gear cannot move.

The planet gears are forced to climb over it. During this
position, the ring gear acts as track for the planet gears to
move over.
The driven shaft which is connected to the planet gear
carrier is thus rotate. When the ring gear is released, it is
free to move in consequence to the rotation of planet gears
which rotate around their axis. During this position, there
is no movement of planet carries and hence the driven
shaft remains stationary. A planetary gear box contains a
numbers of such units to obtain various speed reductions.

S.NO SLIDIND ME GEAR
BOXSH
CONSTANT MESH GEAR
BOX
SYNCHROMESH
GEAR BOX
1. Simplest Design. Better Design Complex Design.
2.
Meshing of gear takes
place by sliding of
gears on each other.
Main shaft gear provided
with dog clutch & sliding
action take place by dog
clutch.
Meshing of Gear
take place by
Synchronize unit.
3.
More change to
damage gear teeth.
Less change to damage gear
teeth.
Very few change to
damage gear teeth.
4. More maintenance.
Less maintenance.
Less More
maintenance.
5.
Quite Satisfactory for
Low speed Car.
Quite Satisfactory for
Medium speed Car.
Quite Satisfactory
for High speed Car.

 Automobile Engineering by “ R.K Rajput” Laxmi
Publications (P) Ltd.
 Automobile Engineering by “Dr. D.S Kumar” S.K Kataria
& Sons Publications (P) Ltd.
 https://www.autodeal.com.ph/articles/car-features/here-
are-different-types-automatic-transmissions
 https://en.wikipedia.org/wiki/List_of_automobiles_with
_continuously_variable_transmissions

 https://en.wikipedia.org/wiki/Direct-shift_gearbox
 https://autoportal.com/articles/types-of-automatic-gear-
shift-levers-you-should-know-about-10168.html

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