How Does a Semi Automatic Gearbox Work?

You’ve heard of manual and automatic cars, but what about semi automatics? These types of cars use a slightly different gearbox to their automatic counterpart to give the driver a completely different driving experience. If you haven’t heard of a semi automatic gearbox, maybe you’ve heard of the term “flappy paddle gear shift”? This is another term used to describe this type of gearbox and gives a hint as to what is involved with this type of transmission. 

Are you curious to learn more about how the semi automatic gearbox works? If so, this blog is for you. As leaders in the automotive industry, Automatic Man has worked with all kinds of automatic gearboxes over the years and this includes semi automatic gearboxes.

We’ll be able to tell you about what they are and how they work, helping you to make an informed decision about the next type of car you want to go for and if a semi automatic gearbox would be the right choice for you.

What is a Semi Automatic Gearbox?

A semi automatic gearbox combines the functions of a manual and an automatic transmission. It has been done to provide the driver with convenient control over gear selection for a smooth driving experience, whilst also giving a feel for what it is like to drive a manual vehicle. 

Essentially, drivers can have the freedom of switching into manual mode by the paddles on the steering wheel and changing the gears like a manual driver would, just without the clutch. The clutch in semi automatic cars is removed, and the functions are performed electronically by the car.

Instead of cables and pipes running from the transmission to the driver so that they can affect gear changes, you have actuators and computers doing all that hard work for you. This is ideal for people who are just looking for a simple and comfortable driving experience, such as when travelling long distances for work.

When you drive a semi automatic car, you will either be presented with a small and simple gear lever with up or downshift changes, or paddles mounted to the outside edges of the steering wheel.

How Does a Semi Automatic Gearbox Work?

Over the years, the operation of semi automatic gearboxes have evolved as different manufacturers experimented with different systems to create the best performing semi automatic gearbox.

Like any other transmission type, semi automatics use the engines kinetic energy to turn the wheels of the car through the rotation of an input shaft and various gears. However, instead of the clutch being accessible in the footwell, it is placed in between the engine and the gearbox.

The semi automatic gearbox changes gears electronically. Since electronic equipment takes care of the clutch, the gearbox can time its gear changes to the torque of the engine and make each gear change fast, precise and smooth.

The computer system in a semi automatic car works to control engine torque, the speed of the car, accelerator pedal position, and some other functions. However, it is mainly used to determine the time and direction of the gear shifting.

The Computer System

This system has been fine-tuned over many years to ensure it remains intuitive and effective. It has the ability to be able to detect when gear-changing is required so it can engage the clutch to disengage the semi-auto transmission from the engine. Once this action has been performed, the shift actuators will activate a gear shifting and disengages the clutch to reestablish the connection between the engine and the transmission.

When it comes to trying to park, reverse or neutralize the transmission, the driver must engage both pedals at once. After this action has been completed, the car will prompt the driver to select one of the three options. 

What Gears Does it Have?

On a traditional automatic car, it will typically have the following gears:

  • P is the parking gear. It locks the transmission.
  • R is the reverse gear. It is similar to R in both traditional manual and fully automatic cars.
  • N is the neutral gear. It is similar to N in both traditional manual and fully automatic cars.
  • D is the drive gear. It is equivalent of D in a fully automatic car. The gearbox in an AMT car is a manual gearbox, instead of one with a torque converter as in a traditional automatic.

However, on the semi automatic gearbox, it could have either push-button or lever controls. Contrary to the automatic gearbox, the semi automatic gearbox 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. This means the average standard layout of a semi automatic gearbox is likely to be Neutral, Reverse, Automatic, and +/- buttons.

Need your Semi Automatic Gearbox Fixing?

Here at Automatic Man, we specialise in the servicing and repairs of automatic gearboxes, and this includes semi automatic gearboxes. If you’re the driver of a semi automatic car and you need your gearbox looking at, get in touch with us to book your car in.
Our expert team will work on your semi automatic gearbox to ensure it is no longer slipping and that is returned to proper working condition. With our latest diagnostic equipment, we can supply parts for almost any transmission, meaning semi automatic gearbox repairs can be carried out quickly and effectively.