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Everything You Wanted To Know About Semi Automatic Transmission

Most of the cars these days function with a manual or an automatic transmission, or an advanced version of either of these two. There is a third variation too, which is called semi automatic transmission. What does semi automatic mean? Well, it features functions from both transmission types; hence, the name has been given. How does this transmission work? How is it different from manual and auto transmissions? Let’s find out the answers in this brief guide.

What Is Semi Automatic Transmission?

Semi auto cars are rare to find in the car these days – thanks to the popularity of the dual-clutch system. However, many models these days come with a dual-clutch/automatic gearbox that the driver can operate in a semi-automatic fashion.

What does semi-automatic mean? It’s not what you guess by the name! It is not automatic in any sense but resembles a manual gearbox without the clutch pedal. If you consider semi automatic vs manual, the only difference between them is that the semi-automatic version uses actuators and computers instead of cables and pipes for shifting the gears.

what does semi automatic mean
Semi-automatic offers the feel of stick shift in an automatic mechanism.

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The main advantages of a semi-auto gearbox are that it facilitates better fuel efficiency (just like a manual transmission) and also as easy to use as an auto gearbox.

How Does A Semi Automatic Transmission Work?

A semi-auto unit follows the working principle of all other transmission types – using engine’s kinetic energy to turn the wheels through the rotation of an input shaft and various gears. There is a clutch in between the engine and the gearbox that allows the latter to engage (when the engine controls it), disengage (when it can spin or not without the engine interference), and partially engage.

A manual transmission uses a pedal to engage and disengage the clutch and a lever for the shifting of gears. Things are slightly different for a semi automatic gearbox that makes use of a set of actuators and a hydraulic motor in the places of a gear lever and clutch pedal, respectively. There is also a control unit (aka computer) that is in the charge of various actions including engine torque, the speed of the car, accelerator pedal position, and some others. It mainly works to determine the time and direction of the gear shifting.

When the control unit detects a situation where gear-changing is required, it engages the clutch to disengage the semi-auto transmission from the engine. Then, the shift actuators will activate a gear shifting and disengages the clutch to reestablish the connection between the engine and the transmission.

The Differences Between Automatic And Semi-Automatic Transmissions

Although their names sound almost similar, these two transmission types are different from each other in a few ways.

The Gear Lever Layout – If an automatic has a gear lever, it will be the typical “PRND” layout (denoting Park, Reverse, Neutral, and Drive). A semi-automatic could have either push-button or lever controls. The gear lever will not have a “Park” mode and there will be an “Automatic” option instead of the “Drive” mode. Most modern cars are likely to have +/- buttons for manual handling of the gear shifting. So, the layout is likely to be Neutral, Reverse, Automatic, and +/- buttons.

semi automatic car
Automatic transmissions are different from semi-automatics.

Functions – An auto transmission changes gear without any input from the driver. All you have to do is to put it in the drive mode and it will then change the gears according to the speed of the car. A semi automatic transmission, on the other hand, will not shift the gears by itself but will help the driver to navigate through gears. The driver has to give inputs for the car to move up or down a gear.

Which Cars Have The Semi Automatic Gearbox?

The semi automatic transmission has been around from the early 1930s. So, it needless to say that you will find this mechanism in the cars of almost all the automakers. Let’s discusses some of the modern car models that use this transmission:

Ferrari – The automaker first used an automated gearbox in their Ferrari Mondial in 1993. The latest version is to be found in the Ferrari 599 GTO. Then, the company chose to use a double-clutch transmission and continued experimenting with it in all of their new models.

Opel – The company uses the Easytronic transmission in a handful of models. You will find it in their smaller cars such as Corsa.

semi auto cars
Opel Corsa uses a semi-auto transmission.

Ford – It first introduced the semi-auto on the 1970 Maverick. It was a regular semi automatic car without the self-shifting option. However, they later developed the SelectShift and then used the Easytronic transmission in some of their smaller cars such as the Fusion and Fiesta.

Honda – Honda’s own version of semi-auto Hondamatic hit the market in the 1970s. It later developed many variations including MultiMatic, S-matic, iShift, and SportShift.

Alpha Romeo – Quite similar to Opel’s Easytronic, Alpha Romeo’s Selespeed transmission is to be found in several models including 156 GTA, Spider, Fiat Punto, Fiat Idea, and more.

Hopefully after reading this article, you will get a clear knowledge about what is semi automatic transmission and the difference between automatic transmission and semi auto transmission. If you have any question about this topic or driving tips, don’t hesitate to leave us a comment in the box below, our auto experts will answer it for you.

3 Comments
  1. Chiyala Mweemba says

    Very interesting and at least I now know the difference even after I have driven a manual, automatic and a semi-automatic cars, l totally was blind on their functioning.

  2. Fred Nandala says

    Thanks for your informative article. My Semi auto vehicle has developed a problem. The gears will engage but the vehicle wont move and shows a sign of park even when the brakes are off. Please advise.
    Fred Nandala

  3. m.censlive says

    dear matsumoto, very good description, but critical analytical inferences on reliability; mttf etc would be the input of a good engineer
    rgds

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