This document provides information on various components of automobile transmissions and gearboxes. It discusses the functions of gearboxes including varying torque ratios for acceleration and climbing gradients. It describes different types of transmissions including sliding mesh gearboxes, constant mesh gearboxes, and gearboxes with synchromesh or dog clutches. Continuously variable transmissions, torque converters, propeller shafts, differentials, axles, and the hotchkiss drive system are also outlined. Electronic transmission controls, overdrive systems, freewheels, universal joints, and power flow through the drivetrain are summarized as well.

1. Automobile Engineering
Unit 2
Clutch and transmission
Ass. Prof. N S Surner
SRES SCOE, Kopargaon

2. Function Of A Gear Box
• Torque ratio between the engine and wheels
to be varied for rapid acceleration and for
climbing gradients.
• It provides means of reversal of vehicle
motion.
• Transmission can be disconnected from
engine by neutral position of gear box

3. Necessity Of Gear Box In An
Automobile
• Variation of resistance to vehicle motion at
various speed.
• Variation of tractive effort at various speed.
• Torque*Speed=Power

4. Total resistance to vehicle motion
i. Resistance due to wind :proportional to the
square of the vehicle speed
ii. Resistance due to gradient: Remains constant
at all speed. This is component of weight parallel
to road
iii. Miscelleneous: Type of the road, tyre friction
etc.

6. Types of Transmission
1. Sliding mesh gear box
2. Constant mesh gear box with positive dog
clutch
3. Constant mesh gear box with synchromesh
device.

11. Epicyclic Gear Train

13. Torque Convertor

14. Basics of Transmission
• The job of the transmission is to change the
speed ratio between the engine and the
wheels of an automobile.
• The transmission uses a range of gears -- from
low to high -- to make more effective use of
the engine's torque as driving conditions
change. The gears can be engaged manually or
automatically.

15. • A continuously variable transmission is also
known as a single-speed transmission, steeples
transmission , pulley transmission, in case of
motorcycles, a twist-and-go is an automatic
transmission that can change seamlessly through
a continuous range of effective gear ratios.
• This contrasts with other mechanical
transmissions that offer a fixed number of gear
ratios. The flexibility of a CVT allows the input
shaft to maintain a constant angular velocity

17. CVT Design
• Pulley based CVT
• Toroidal CVT
• Hydrostatic CVT

18. Benefits of CVT
• Provide engine torque in optimum condition
(road loads / drive shaft torque)
• No shift clonk
• Transmission ratio can be adjusted
continuously
• Improved fuel efficiency
• Better acceleration
• Eliminates gear hunting especially when going
up a hill.

20. • A belt-driven design offers approximately 88%
efficiency.

21. Electronic transmission control
• Modern transmissions are hydraulically operated
with electronic controls. These controls provide:
• A better correlation between the engine and
transmission
• Improved shift timing control
• Improved shift quality control
• Ability to provide driver-selected economy or
performance operation
• Improved ability to determine proper
transmission operation

22. • An electronic control system has three major
portions:
1. The inputs provide needed information.
2. The controller processes information and
activates the outputs.
3. The outputs do the work.

24. Overdrive
• This device helps the propeller shaft to rotate
faster than the engine in transmission.
• By its use engine revolutions can be reduced by
20-25% allowing high cruising at lower engine
revolution.
• An overdrive is usually fitted to the top or third
and top gear only.
• It can be operated manually or automatically.
• The overdrive unit consist of epicyclic gears when
fitted at rear of the gear box.

27. Freewheel
• One way clutch, transmit power in one
direction only, ex bicycle….

28. Propeller shaft

29. • Shaft
– Withstand torsional load
– Well balanced to avoid whirling at high speed
– Steel, Al or composite material
• Universal Joint
– Accounts up and down motion of the rear axle
– Cardon joints- high speed constant velocity joint with
the option of intermediate bearing ,limited slip devices
and crash feature
• Slip Joint
– Adjust the length of the propeller shaft

30. Constant velocity joint
• Generally used for front wheel drive
• Two types
• Fixed type (outboard): at wheel end
• Plunging types (inboard): at differential end

31. Axle shaft
• Transmits power from inner to outer CV-joint

32. Rzeppa Joint - Exploded View

33. Final Drive
• Final drive is the last stage of power transfer from propeller
shaft to rear (or front if – automobile is front wheel driven)
axles and then to wheels. It turns the propeller shaft
motion at right angle to drive the rear axle.
• Consists of Bevel pinion and crown wheel or worm and
worm wheel arrangement
• Bevel gear=propeller shaft
• Crown wheel drive goes to the differential
• Three Types of the gears are used
• Straight Bevel Gears (uneven transfer of motion)
• Spiral bevel gears
• Hypoid bevel gears

34. Differential
• Pinion Drive Gear: transfers power from the driveshaft to the ring
gear.
• Ring Gear: transfers power to the Differential case assembly.
• Side/spider gears: help both wheels to turn independently when
turning.
• Differential case assembly: holds the Ring gear and other
components that drive the rear axle.
• Rear drive axles: steel shafts that transfer torque from the
differential assembly to the drive wheels.
• Rear axle bearings: ball or roller bearings that fit between the axles
and the inside of the axle housing.
• Axle housing: metal body that encloses and supports parts of the
rear axle assembly.

36. Power flow
• Drive shaft spins the Pinion gear.
• Pinion gear turns the larger ring gear to
produce gear reduction.
• Ring gear attached to differential case, hence
it rotates with the ring gear.
• Differential case spins the sun gears which are
attached to the axles.
• Axles transfer the power to the wheels.

37. Function
• Transfers power from driveshaft to the
wheels.
• Provides final gear reduction.
• Splits amount of torque going to each wheel.
• Allow the wheels to rotate at different speeds
in turns.

38. Hotchkiss Drive
• The Hotchkiss drive is a system of power
transmission
• Rear axle drive
• It was the dominant form of power
transmission for front-engine, rear-wheel
drive layout cars in the 20th century
• Requirement of mechanism to transfer driving
and braking efforts to chassis

39. Construction of Hotchkiss Drive
• Simplest and most widely used type of rear axle
drive .
• The spring besides taking weight of the body also
take the torque reaction , driving thrust and side
thrust.
• Propellar shaft is provied with two universal
joints also a sliding joint .
• The front end of the spring is fixed rigidly on the
frame while the rear end and is supported in the
shackle .

42. Torque Tube