Summary of Automatic vs Manual Transmission
Manual
Gear sets are on two shafts.
Gear change is via a clutch.
Driver selects gears manually with a floor
shifter,
Automatic
A combination of planetary gear sets
Gear change is via a clutch packs which
operate automatically without driver
invention.
Gear selection is done automatically based on
the engine RPM
In the last decade there have been many variations in automatic transmissions. Some just relate to
the driver interface while other variations are in the internal design of the transmission.
Manumatic Transmission
Manumatic as the name suggests is a type of automatic transmission that allows the driver to
select gears manually using a gear shifter or Paddle shifters mounted on the steering wheel. This is
ideal for towing or off road driving situations. The tiptronic by Porsche was one of the early
manumatic transmission systems.
Continuous Variable Transmissions (CVT)
A CVT transmission is different to a conventional automatic transmission by having no fixed gears.
There are two pulleys, one connected to the engine shaft and the other connected to the drive
shaft. The two pulleys are connected by a belt. Each pulley can vary its diameter independently
according to the demand of the engine, thus creating an infinite number of gears. CVT
transmissions have the following advantages;
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Smother acceleration
Linear Response
No gear hunting
Constant engine RPM
The disadvantages;
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Less engine engagement, hence driving experience
Drone sound when accelerating
CVT transmissions can also have a manual shifting mode which sets the gear ratios in fixed
positions giving the driver a better driving experience.
Direct Shift Gearbox (DSG)
The DSG transmission is made up of two independent gearbox units with matching clutches.
Typically one gearbox engages the odd gears and the other the even gears. Both gearboxes are
connected to the engine via two drive shafts. Each clutch is operated by a hydraulic actuator
allowing gear changes to be changed without any reduction in traction.
The DSG transmission unit contains an electronic unit and sensors, to predict and prepare for the
next gear change.
DSG transmissions can also be operated in manual mode allowing he driver to change gears using
gear shift paddles or a gear shift lever.
Advantages of DSG transmissions are;
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Consistent power delivery
Optimum efficiency translating to better fuel economy