Nostalgia. Assignment for seminar in Prof. Rajat Mehrotra's class. Those days citing sources in presentation was not the norm. Image credits are from my then night time love website CarBibles.com of old. It can be accessed on Internet Archive. It was a treasure trove of automotive information lighting a seekers mind first time to the anatomy of automotive technology. https://web.archive.org/web/20090224063513/http://www.carbibles.com/suspension_bible.html Countless late hours were spend devouring every word replaying every animation reading every updated chapter religiously. I hope Chris rides the bike of his dreams now.

2. INTRODUCTION
An automatic transmission (commonly "AT" or
"Auto") is an automobile gearbox that can
change gear ratios automatically as the vehicle
moves, freeing the driver from having to shift
gears manually.
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.

3. COMPARISON WITH MANUAL
TRANSMISSION
In most Asian markets except the Indian
subcontinent, automatic transmissions have
become very popular since the 1990s. Most cars
sold in the United States since the 1950s have
been equipped with an automatic transmission.
However, manual transmissions are more
popular than automatics in Europe.

4. HISTORYAND IMPROVEMENTS 1
1904 Sturtevant brothers of Boston, Massachusetts. This unit had two forward
speeds, the ratio change being brought about by flyweights that were driven
by the engine.
1908 Henry Ford's remarkable Model T. The Model T, in addition to being
cheap and reliable by the standards of the day, featured a simple, two speed
plus reverse planetary transmission.
1934 General Motors developed semi-automatic transmissions that were less
difficult to operate than a fully manual unit.
1939 Chrysler Corporation's work on adapting the fluid coupling to automotive
use.
1940 Available as an option on 1940 Oldsmobiles and later Cadillacs, the
Hydra-Matic combined a fluid coupling with three hydraulically-controlled
planetary gearsets to produce four forward speeds plus reverse.
1956 GM introduced the "Jetaway" Hydra-Matic, which was different in design
than the older model.
1959 Borg-Warner developed a series of three-speed torque converter
automatics for American Motors Corporation, Ford Motor Company,
Studebaker.

5. HISTORYAND IMPROVEMENTS 2
1980s whale oil was removed from automatic transmission
fluid. eventually replaced by overdrive-equipped
transmissions providing four or more forward speeds. Many
transmissions also adopted the lock-up torque converter
2000s ZF Friedrichshafen AG and BMW were responsible for
introducing the first six-speed (the ZF 6HP26 in the 2002
BMW E65 7-Series). Mercedes-Benz's 7G-Tronic was the first
seven-speed in 2003, with Toyota Motor Company introducing
an 8-speed in 2007 on the Lexus LS 460.

7. MAJOR TRANSMISSION COMPONENTS
Torque converter
Planetary gear unit
Clutches and bands
Hydraulic control unit

8. MAJOR TRANSMISSION COMPONENTS

9. MAJOR TRANSMISSION COMPONENTS

10. Torque converter
Planetary gear unit
Clutches and bands
Hydraulic control unit

11. TORQUE CONVERTER
The key to the modern automatic transmission is the torque converter. It takes the place of a clutch in a
manual transmission.
A direct descendant of an earlier component called a fluid coupling, the torque converter offers the
advantage of multiplying the turning power provided by the engine. It is connected to the motor by
means of a metal rod known as the transmission shaft (sometimes called the input shaft), which fits next
to but does not touch the engine crankshaft.
Repeat: there is no direct connection between the engine and the transmission.
Instead, the engine turns the transmission by means of a process called hydraulic coupling.

12. A torque converter has three stages of operation:
• Stall. The prime mover is applying power to the pump but the turbine
cannot rotate. For example, in an automobile, this stage of operation
would occur when the driver has placed the transmission in gear but is
preventing the vehicle from moving by continuing to apply the brakes. At
stall, the torque converter can produce maximum torque multiplication
if sufficient input power is applied (the resulting multiplication is called
thestall ratio). The stall phase actually lasts for a brief period when the
load (e.g., vehicle) initially starts to move, as there will be a very large
difference between pump and turbine speed.
• Acceleration. The load is accelerating but there still is a relatively large
difference between pump and turbine speed. Under this condition, the
converter will produce torque multiplication that is less than what could
be achieved under stall conditions. The amount of multiplication will
depend upon the actual difference between pump and turbine speed, as
well as various other design factors.
• Coupling. The turbine has reached approximately 90 percent of the
speed of the pump. Torque multiplication has essentially ceased and the
torque converter is behaving in a manner similar to a plain fluid
coupling. In modern automotive applications, it is usually at this stage of
operation where the lock-up clutch is applied, a procedure that tends to
improve fuel efficiency.

14. Torque converter
Planetary gear unit
Clutches and bands
Hydraulic control unit

15. PLANETARY GEAR

16. PLANETARY GEAR

18. Compound Planetary Gearset
This automatic transmission uses a set of gears, called
a compound planetary gearset, that looks like a single
planetary gearset but actually behaves like two
planetary gearsets combined. It has one ring gear that
is always the output of the transmission, but it has two
sun gears and two sets of planets.

19. The figure below shows the
planets in the planet carrier.
Notice how the planet on the
right sits lower than the
planet on the left. The planet
on the right does not engage
the ring gear -- it engages the
other planet. Only the planet
on the left engages the ring
gear.
Next you can see the inside
of the planet carrier. The
shorter gears are engaged
only by the smaller sun gear.
The longer planets are
engaged by the bigger sun
gear and by the smaller
planets.

20. Torque converter
Planetary gear unit
Clutches and bands
Hydraulic control unit

21. CLUTCHES AND BANDS

22. MULTIPLATE
CLUTCH

23. BAND BRAKE

24. PARKING PAWL
AND
ONE WAY
CLUTCH

25. PARKING MECHANISM
The output of the transmission: The square
notches are engaged by the parking-brake
mechanism to hold the car still.
The empty housing of the transmission with the parking
brake mechanism poking through, as it does when the
car is in park
This rod actuates the park mechanism.
Top view of the park mechanism

26. Torque converter
Planetary gear unit
Clutches and bands
Hydraulic control unit

27. HYDRAULIC CONTROL UNIT
Above you can see two pistons that actuate the bands. Hydraulic
pressure, routed into the cylinder by a set of valves, causes the
pistons to push on the bands, locking that part of the gear train to
the housing.
They're used to pressurise the piston plate for the clutches and they're
used to move the band-activation pistons up and down.

28. Automatic transmission modes

29. Automatic transmission modes
Vehicles conforming to standards must have the modes
ordered P-R-N-D-L (left to right, top to bottom, or
clockwise). Prior to this, quadrant-selected automatic
transmissions often utilized a P-N-D-L-R layout, or similar.
Such a pattern led to a number of deaths and injuries
owing to unintentional gear mis-selection, as well the
danger of having a selector (when worn) jump into Reverse
from Low gear during engine braking maneuvers.
Park (P) – This selection mechanically locks the
transmission, restricting the car from moving in any
direction.
Reverse (R) – This puts the car into the reverse gear, giving
the ability for the car to drive backwards.
Neutral/No gear (N)– This disconnects the transmission
from the wheels so the car can move freely under its own
weight.
Drive (D)– This allows the car to move forward and
accelerate through its range of gears. The number of gears
a transmission has depends on the model, but they can
commonly range from 3 (predominant before the 1990s),
4, 5 to now 6,7 or even 8.

30. INSIDE AN AUDI TRANSMISSION

31. POWER FLOW

37. DIFFERENCE BETWEEN D AND L
RANGE FIRST GEAR

38. OTHER TECHNOLOGIES
TipTronic® Gearboxes
In normal operation, we use the gearbox just like an automatic, putting it in 'D'
for Drive and just letting it go about its business. But if we click the gearstick
over into the H-gate it becomes a discrete automatic, meaning we can then
click it fowards and backwards like a sequential gearchange. In this mode
we are basically telling the gearbox when we want it to shift rather than
allowing it to shift for us.
Semi-automatic Gearboxes
With this type, the action of moving the gearstick out of the gate for one of the
gears (for example pulling it back from first) passes a hall effect sensor
which tells the clutch to disengage. When you push the gearstick into the
gate for the new gear, another hall effect sensor detects the final position of
the gearstick and tells the clutch to re-engage. Effectively it's identical to
driving a manual car only without a clutch pedal.
DSG / DCT Gearboxes
The idea is that when you're going up through the gears, increasing in speed,
one clutch has the current gear engaged and a second clutch has the next
gear up pre-engaged ready to use in the blink of an eye.

39. OTHER TECHNOLOGIES
CVT (continuously variable transmission)
Toroidal CVT (Nissan Extroid)

40. AUTOMATIC TRANSMISSION MODELS
Some of the best known automatic transmission families include:
General Motors — Powerglide, "Turbo-Hydramatic" TH350, TH400 and
700R4, 4L60-E, 4L80-E, Holden Trimatic
Ford: Cruise-O-Matic, C4, C6, AOD/AODE, E4OD, ATX, AXOD/AX4S/AX4N
Chrysler: TorqueFlite 727 and 904, A500, A518, 45RFE, 545RFE
BorgWarner (later Aisin AW)
ZF Friedrichshafen
Allison Transmission
Voith Turbo
Aisin AW; Aisin AW is a Japanese automotive parts supplier, known for its
automatic transmissions and navigation systems
Honda
Nissan/Jatco
Volkswagen - 01M
Drivetrain Systems International (DSI) - M93, M97 and M74 4speeds, M78
and M79 6Speeds

41. A.T. CARS IN INDIA
• Maruti Udyog offers the automatic transmission
options in the Zen, the Wagon R and the Esteem, all of
which feature a three-speed automatic. Prices range
from about Rs 4.9 lakh for the Zen AT to about Rs 6.35
lakh for the Esteem AX.
• Hyundai offers automatic transmission on two of its car
models — the Santro Xing in the small car segment
priced at Rs 4.26 lakh (ex-showroom) and an H-matic
four-speed auto transmission in the Sonata 2.7 V6
variant priced at Rs 15.2 lakh.
• Toyota offers AT in Corolla and Camry.
• Skoda Octavia, Laura and Superb.