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Basics Of Automobile Engineering – Transmission system and Types Of transmission systems

What is Automobile Transmission System

In an automobile, engine is the main source for developing the power and the power produced from it must be transmitted to the wheels of the vehicle to move it from one place to another. The system which is developed for transmitting the power from the engine to the wheels of the vehicle is called as the automobile transmission system or vehicle power transmission system. For basic needs of the vehicle and for space requirements,the manufacturers place the engines in appropriate locations and transmit the energy from the engine to the wheels by various ways. Let us discuss some of the ways how the power is transmitted to the wheels with suitable diagrams.

Transmission system

In automobiles the rotary power
(or torque) is obtained from the engine.The developed power is transmitted to the rotating wheels on the road. The unit which has various components connected in between the engine and the rear wheels of the vehicle is called as the automobile power transmission system. Let us see the important parts of an automobile transmission system.

Parts of Transmission System

1. Clutch
2. Gear box
3. Propeller shaft
4. Universal joint
5. Differential
6. Rear axle

Needs of transmission system

• For transmitting and stopping torque developed from the engine to the rear axle of the vehicle.
• For transmitting power to wheels without any noise during the engine is running.
• For avoiding vibrational effects during the transmission of power from engine to the rear wheels.
• For operating the vehicle wheels at the required speed.
• For balancing the speed of the wheels during vehicle is in running.

Types of transmission system

1. Front Engine Rear Wheel Drive
2. Front Engine Front Wheel Drive
3. Front Engine Four Wheel Drive
4. Rear Engine Rear Wheel Drive

Front engine rear wheel drive

Generally front engine rear wheel
drive is commonly used in most of the
vehicles. The power from the engine tothe running wheels is transmitted through the clutch, gearbox, universal joint and the differential unit. The front engine rear wheel drive is shown in figure


• Engine cooling is good
• Vehicle’s weight is evenly distributed
• It is easy to connect the components
with the engine
• It is easy to control the vehicle


• Lengthy propeller shaft is needed
• Vehicle’s ground clearance is high
• Vehicle’s stability is low.

Front engine front wheel drive

In front engine front wheel drive,
the clutch, gearbox and the differential unit are made as an integral part. The engine’s power is transmitted to the front wheels by means of the clutch,gearbox,differential and small shaft. Propeller shaft is not necessary in such drives for transmitting the power. Two pairs of constant velocity
universal joints are used in front axle.The first one is located near the differential and another one is kept near the stub axle.To Transfer power with require angle and to transmit the steering power to the wheel these joints are being used. This type of drive is used in modern vehicles.Its construction is shown in figure


• Simple in design
• Have high stability

• Good road grip
• High engine cooling
• Good control over the vehicle
• There is no need of a separate propeller shaft


• Maintenance cost is high
• Road grip is less when the vehicle is
driven in slope or slanting regions
• Due to the engine’s exhaust,passengers gets affected

Front engine four wheel drive

Four wheel drive is the one in
which the engine’s power is transmitted to all the four wheels at a time. The fourwheel drive consists of two differential units, four universal joints, one constant velocity universal joint, a propeller shaft and a transfer case.In four wheel drive the engine’s
power is transmitted to the transfer case by clutch, gearbox and a small shaft.From the transfer case the power is being transferred through two propeller shafts to front and rear axle differentials, from that the power is finally transmitted to all the four wheels. In such operation high power is obtained hence four wheel drives are more suitable for mud and wet
roads. Mostly four wheel drives are usedin military vehicles, Jeep, special vehicles and foreign vehicles


• Pulling power is more
• Can operate vehicles in water, mud,
clay and slime areas also
• Sometimes if one wheel fails to
function, vehicles can operate using
other three wheels


• Initial cost is high
• Maintenance is high
• Complicated design
• Create more noise
• Vibration is more

Rear engine rear wheel drive

In the rear engine rear wheel drive
clutch, gearbox and differential unit are made as a single unit. The engine power is transferred to rear wheel by means of the clutch, gearbox, differential and a small shaft.Propeller Shaft is not used.In this type of drive placing the engine’s exhaust system is easy. As the driver is sitting in the front it is difficult to control clutch and gearbox. The drive needs long linkages in this type of drive


• Simple in design
• Separate propeller shaft is not
• Brake power is high
• No problem to passengers because of
• No need for lengthy propeller shaft


• Stability is less
• Long linkages are needed
• Maintenance is high
• Engine cooling is less.

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