What Is a Sequential Gearbox?

Mainly used in sports and race cars, a sequential gearbox lets you change gear manually, thereby giving you a faster shift.

Read on to learn what a sequential gearbox is, and what the benefits of this type of transmission are. 

 

What Is a Sequential Gearbox?

Certain vehicles, namely race cars and motorcycles, use a transmission known as a sequential gearbox - or sequential manual transmission - which allows you to shift gears manually. You are unlikely to find a sequential gearbox in a conventional car, though some cars with manual transmissions can be upgraded to include a sequential gearbox to improve the vehicle’s performance. This tends to be the case with higher-end cars.

 

How Does a Sequential Gearbox Differ From a Normal Manual Transmission?

Though a sequential gearbox is similar to conventional automatic and manual transmissions, there are some key differences. Whilst a manual transmission moves in a H-pattern, the lever from a sequential manual transmission instead moves only backwards and forwards. 

What’s more, drivers of vehicles which use a sequential manual transmission will be able to change gears without involving the clutch - unlike drivers of traditional manual vehicles. Though, the driver cannot skip between gears - you may only select gears in the pre-existing pattern.

 

Components of a Sequential Gearbox

A sequential transmission uses a dog box transmission and a dog clutch. A gear selector fork is used to force the transmission into gear, by engaging the dog clutch. The dog clutch uses interference rather than friction discs - as with a traditional clutch -  enabling two shafts to rotate.

Though the vehicle will have one, it is not always necessary to use the clutch, as dog clutches only need a moment without torque in order to shift. As such, a multi-plate clutch can connect or disconnect engine torque depending on what you want the vehicle to do. The clutch need only be used to move from a standstill when the car is driving hard.

The selector pin can be found on the gear selector fork, and helps the selector to navigate the grooves on the selector shaft. The selector forks connect to this shaft, and the sequential gear selector turns this selector shaft. 

In other words, a driver can select a gear, but only in a sequence - you cannot move from, for example, 6th to 3rd gear as with a manual transmission. 

To shift gears in a vehicle with a sequential transmission, you can use a conventional lever, buttons, or steering wheel mounted paddles. 

 

Advantages of a Sequential Gearbox

A sequential gearbox allows for quicker gear shifts than that of a manual vehicle, and negates the need to depress and release the clutch pedal. This is particularly beneficial when it comes to motor racing, as the driver can save precious seconds during a race that these actions would require. The driver need simply push or pull the gear lever in order to shift gear almost instantly.

Sequential manual transmissions also weigh less and take up less space than dual-clutch transmission systems do, due to the fact that they are made up of fewer component parts and have a lighter flywheel. As you can probably imagine, this is another advantage when it comes to motorsports racing. 

Compared to the H-pattern of a manual transmission, a driver using a sequential transmission vehicle will also save time when it comes to shifting gears - as they will not have to make a decision as to which gear to select. This is a bonus as the driver will never run the risk of blowing up the engine by mis-shifting during a race as with a traditional manual transmission. 

Overall, a sequential gearbox can be easier to control than a conventional manual transmission. A sequential gearbox can give you a smoother driving experience, with enhanced performance and ease when shifting gears.

 

Disadvantages of a Sequential Gearbox

On the downside, sequential gearboxes can be extremely noisy, and whilst they can make shifting gears easier, the drive isn’t always smooth if travelling at too slow a speed. This can explain why sequential gearboxes are rarely fitted to regular cars you see on the road.

Another important disadvantage to mention is the fact that a sequential transmission will need to be rebuilt after the first few thousand miles, due to the fact that they will naturally experience wear and tear during races. Not to mention the high upfront cost of a sequential transmission, which can be several hundreds of pounds before factoring in the maintenance and installation costs. 

 

We hope that this article has taught you a thing or two about sequential gearbox transmissions. Whether or not your vehicle actually uses a sequential gearbox transmission, you’ll want to take good care of your car all the same. Book in for a service at a time that suits you, and enjoy a smooth driving experience today.