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How does an Automatic Transmission Work?

This is Flash animation of Automatic transmission. Automatic transmissions use planetary gear system to operate.

Please Also watch our YouTube video for more information about Automatic Transmission.

Fallowing descriptive images are taken from Garagevitesse web site


Power input: ring gear
Power output: planetary carrier

Stationary: sun gear
When the sun gear is held stationary, only the
pinion gear rotates and revolves. Therefore, the
output shaft decelerates in proportion to the input
shaft only by the rotation of the pinion gear.
Direct Coupling

Power input: sun gear, ring gear
Power output: planetary carrier

Ring gear rotates with the locked planetary carrier,
the input and output shafts rotate at the same rate.
Reverse Rotation

Power input: sun gear
Power output: ring gear

Stationary: Planetary carrier
When the planetary carrier is fixed in position and
the sun gear turns, the ring gear turn on its axis
and the rotational direction is reversed.

The reference uses a model to explain the operation using different input and output shafts. In an actual vehicle, the construction is more complex in order to enable the planetary gear unit to appropriately shift gears, as shown by the left diagram.

Ukasha yusuf
01 Dec 2012

I am very happy with this service and sure that there is no one like you thanks

29 Dec 2012

Thank u so much for the video..

10 Jan 2013

excellent description
to what could easily be a complicated answer

17 Jan 2013

i am so happy to see that but want to know how does reverse gear work

20 Jan 2013

Its super

27 Jan 2013

it really works

04 Feb 2013

dear sir
input power planetary gear and output power sun gear and ring gear is fix what retio

21 Apr 2013

really amazing animation understand

24 May 2013

Hi sir.

I am a commercial instructor in Brazil.
First to all, this animation is very good and I would like to use it in my classes. So I would like to Know if it's possible for you to send me this animation in flash player? If it's OK. Can I use in my classes?
Best regards


25 May 2013

Awe ilabomba bwino.

Chris Dunn
10 Jun 2013

Nice job, thank you

11 Jun 2013

very good for learners

gurdial singh
28 Jun 2013

very good animations

05 Jul 2013

very nicely explained.

14 Jul 2013

hola ademas de mecánico doy lecciones como puedo conseguir este me seria muy útil gracias esta muy bueno

Joydeb Dasgupta
18 Aug 2013

Could you make an animation showing the torque converter and the propeller shaft also ,including the ring gear drive

25 Aug 2013

Could you share this program, to use it off-line?
I have also a suggestion: could you make two inputs variables (with different speeds) and one exit variable?
for instance, if I explain the first gear of an AT, I can say that carrier is conected to output shaft, sun is the input and the ring is locked. The second gear, there are other planetaries that would speed up the ring gear, but less than the sun, that still spins at same rotation than the turbine. This arrangement provides a second gear. A third we could have 1:1, where the sun and ring are at same rotation, and at last, the 4th gear (in a 4-gear AT), the other planetaries would make the ring to spin at a higher rotation than the sun, which always spins at same turbine speed. This combination would provide an overdrive.
In summary, I would like to explain with one planetary how we could combine several planetaries gearsets.


25 Aug 2013

Also... I would love to see how torque converter works, in such simulation system (impeller, turbine and stator, explaining the torque multiplication, from max torque multiplication to the minimal, when lockup applies.

Excellent work!, really nice!

01 Sep 2013

I love this illustration diagram please i want to become an expert in auto transmission pleas i need textbooks about it and some articles that can help me if u can send it to my email i will appreciate and e books

02 Sep 2013

thank u so much for increasing my knowledge

06 Sep 2013

Explanation is very clear

mr daus
11 Sep 2013

Assalamualaikum.. molek mena penjelasan demo buat... mudah pehe sikit..

Information Seeker
16 Sep 2013


Your animations are awesome but I was wondering if you have any information that you are willing to share about how this is theory is applied in real life?

Thank You

19 Sep 2013

very very nice..................

jaswant singh
16 Oct 2013


muse amsalu
18 Nov 2013

i am so happy to see that........

24 Nov 2013

i hope that if you can explain theory under animation would be a great for beginner

23 Jan 2014

Great animation,
I am a professor at an engineering school,
i would like to show this to my students.
Is it possible to have the video?

Thanking you in advance

19 Feb 2014

its very good excellent description for knowledge..

02 Mar 2014

Nice Tutorial

eddie cenabre
15 May 2014

Excellent presentation any body can understand the movement of all the parts inside the automatic transmission.

16 May 2014

very very nice

17 May 2014

excellent description for knowledge..

11 Jul 2014

very nice

kapila hemakeerthi
20 Jul 2014

Very very thank's you'r prasantation

26 Jul 2014

but how they fixe planet n other gers can shere the video how dp they do ????

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