What is the difference between automatic and semi-automatic transmission?

Decades ago, the majority of the automakers provided both manual and automatic drivetrains, whereby most consumers preferred the manual option as it was over$1000 cheaper and easier to maintain. As the years went by, car manufacturers made automatic transmission easier to maintain, and people got used to the ease of electronic shifting.

Automated vehicles gained favor among the masses, and manufacturers began saving money by offering only one drivetrain option. Similarly, semi-automatic transmissions are quite rare to find due to the invention of dual-clutch systems. So, what are the differences between automatic and semi-automatic transmissions?

What does semi-automatic mean?

A semi-automatic transmission is an automated manual gearbox. Unlike manual transmission, semi-automatic gearboxes use computers and actuators when shifting gears, instead of a clutch. Many modern vehicles with automatic gearbox can be operated in a semi-automatic manner if the driver opts to do so.

The driver makes gear changes as they would in manual transmission by pulling paddle shifters, but without the use of a clutch pedal. In semi-automatic transmissions, the function of the clutch pedal is performed electronically; hence, it might not be as fast and smooth as the driver would want.

In automatic transmissions, the vehicle performs all the functions in gear shifting. By using a planetary gear set to produce different gear ratios, the transmission adjusts the gears automatically based on engine speed. Automatic transmissions give less control to the driver but offer exceptional comfort and convenience. 

How does a semi-automatic transmission work?

Semi-automatic transmissions are manual transmissions without the clutch pedal. This transmission system uses the engine’s kinetic energy to turn the wheels by rotating various gears and the input shaft.

In such transmission systems, the clutch exists between the gearbox and the engine, enabling the gearbox to engage, disengage or partially disengage, depending on the engine’s interference. Semi-automatic transmissions use a set of processors and actuators, instead of the clutch pedal and gear lever in manual transmissions.

They also have a control unit (computer system) that controls various actions, including the speed of the car, engine torque, and accelerator pedal position, among many others.  The primary function of the control unit is to determine the direction and time of gear shifting.

Once the control unit detects a need for a gear change, it engages the electronic processors and actuators to disengage the semi-automatic transmission from the engine, activating gear shifting and disengaging the clutch to re-establish the connection between the transmission and the engine.

You may be wondering then, what is the point of owning a semi-automatic vehicle? Well, semi-automatic transmissions allow the driver to have the convenience and comfort found in automatic transmissions, while also enjoying some of the benefits of a manual transmission, such as gear shifting and transmission braking.

What is the purpose of paddle shifters?

purpose of paddle shifters

Paddle shifters, also known as flappy paddles, are usually attached to the back of the car’s steering wheel, or mounted on the steering column itself, in semi-automatic transmissions.

They allow drivers to electrically shift their semi-automatic transmission system by pulling on the paddle itself. In other words, they simulate a clutchless manual transmission

In most vehicles, the paddle on the right upshifts (changes the gear to a higher one when speeding up) and the paddle on the left downshifts (shifts to a lower gear when slowing down). Semi-automatic transmissions have one set of clutches control the odd gears (1, 3, 5, 7) while the other set controls even gears (2, 4, 6, 8).

How do paddle shifters work?

Paddle shifters can be engaged at any time when the transmission is set to Drive. By tapping or pulling the levers, you upshift or downshift, making the transmission to hold the chosen gear for a few seconds and then revert to its automatic nature.

Vehicles with paddle shifters have a different steering wheel as compared to vehicles with other transmission systems, giving room for paddle shifters on both sides of the wheel. As you pull the levers to shift the gears, a corresponding number flashes up on the dashboard, indicating your selected gear. Drivers can also opt to pull the shifter twice to work up or down the gears more quickly.

 Pros of semi-automatic transmission

Semi-automatic transmissions offer drivers an easier time and a better driving experience when shifting gears. The gear shifting process is smooth and occurs quite quickly.

New drivers who do not want to learn driving via manual transmission are advised to use a semi-automatic first. It assists them in learning when to shift gears and how to listen to the engine’s RPMs, without needing to disconnect the clutch.

Another advantage of semi-automatic transmissions is that they are better for the environment. There is no energy loss if there is slippage in the torque converters – this is also happens in manual transmissions.

Cons of semi-automatic transmissions

Semi-automatic transmissions offer an unforgettable driving experience, despite its few disadvantages. Semi-automatic cars are more expensive as compared to manual vehicles.

The electronic components that make up the semi-automatic transmission system are more sophisticated to manufacture; thus, an increase in the price that the car buyer pays.

Similarly, semi-automatic transmissions tend to fail and frequently malfunction as compared to manual transmissions. The transmission itself does not have to experience an issue for the system to malfunction. As a result, the cost to repair such parts is very expensive that their replacement is cheaper.

Can you drive a semi-automatic car like an automatic?

Semi-automatic vehicles have an automatic gear change option as well. Once you hold a gear too long in semi-automatic transmissions, the transmission will switch to auto mode and the control unit will override your gearing request. this prevents the catastrophic failure of the components of your transmission.

Similarly, once you put the gearbox on Drive, the control unit takes over; hence, you do not need to touch the gear shift again until you want to reverse or park the car. Having the option of paddle shifters allows you to have more manual control whenever you deem fit.

Conclusion

If money is not an issue when buying a vehicle, then you can comfortably buy a semi-automatic vehicle. By learning the differences between an automatic and semi-automatic transmission, consumers are more aware of their choices when purchasing cars. It depends on whether you want complete control, partial control, or no control at all during your driving experience.

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