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Outomatic Transmission

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.