- The document presents a seminar on automatic transmissions, beginning with an introduction comparing them to manual transmissions. - Automatic transmissions use planetary gearsets rather than compound gearsets used in manual transmissions, and do not require a clutch pedal or gear shifting by the driver. - The major components of an automatic transmission include an ingenious planetary gearset, bands to lock parts of the gearset, wet-plate clutches, a hydraulic system to control the clutches and bands, and a large gear pump.

1. A SEMINAR ON
AUTOMATIC
TRANMISSION
Presented by
Shubham Kumar Gupta
Roll no. 13/ME/143
Department of
Mechanical Engineering

2. IN THIS PRESENTATION……
Introduction
How automatic transmission varies with manual?
Major components
Mechanism of six speed automatic transmission
gearbox
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3. INTRODUCTION
An automatic transmission, also called auto, self-
shifting transmission or AT, is a type of motor
vehicle transmission that can automatically change gear
ratios as the vehicle moves, freeing the driver from having
to shift gears manually. Both the automatic transmission
(plus its torque converter) and a manual
transmission (with its clutch) accomplish exactly the same
thing, but they do it in totally different ways.
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4. Different from manual
transmission….Manual transmission uses compound gearset whereas
automatic transmission uses epicyclic/planetary gearset.
There is no clutch pedal in an automatic transmission
car.
There is no gear shift in an automatic transmission car.
Once you put the transmission into drive, everything else
is automatic.
Manual transmission locks and unlocks different sets
of gears to the output shaft to achieve the various gear
ratios, while in an automatic transmission, the same set
of gears produces all of the different gear ratios.
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5. Figure: manual transmission
Figure: manual shift
stick
Figure: automatic transmission
Figure: automatic
shift stick 5

6. MAJOR COMPONENTS OF AUTOMATIC
TRANSMISSION MECHNIASM
When you take apart and look inside an automatic
transmission, you find a huge assortment of parts in a fairly
small space. Among other things, you see:
An ingenious planetary gearset.
A set of bands to lock parts of a gearset.
A set of three wet-plate clutches to lock other parts of the
gearset.
An incredibly odd hydraulic system that controls the
clutches and bands.
A large gear pump to move transmission fluid around.
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7. Any planetary gearset has three main components:
 The sun gear
 The planet gears and the planet gears' carrier
 The ring gear
Each of these three components can be the input, the output or can
be held stationary. Choosing which piece plays which role
determines the gear ratio for the gearset.
Figure: from left to right, the ring gear, planet carrier, and two sun
gears
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9. OPERATION OF AN AUTOMATIC
TRANSMISSIONIn an automatic transmission there are basically two inputs given to sun and ring
gear and one output taken from planet carrier.
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