Sequential Transmission – Only For Race Cars?

Sequential Transmission – Only For Race Cars?

Have you ever attended a motorsport event? If so, have you ever wondered why those cars make a whining noise when they move? What if I told you that the engine is not the source of it. In fact, the source of this noise is the sequential transmission system of these vehicles. In this article, we will tell you all you need to know about it!

These transmissions differ from traditional automatic and manual transmissions in many ways. However, these technologies share some similarities as well. The primary users of this transmission type are race cars. But, some car manufacturers have implemented this technology in their road-legal vehicles as well. This transmission system is a very popular performance modification as well.

After this introduction, you may have some doubts about this transmission system. Well, we are here to answer all your doubts and questions. So, without further ado, let’s proceed with our discussion. We will start off by looking at the basics of this transmission.

Sequential Manual Transmission

Sequential transmissions are an evolution of the traditional manual transmission system. Due to this reason, they are sometimes called sequential manual transmission as well. The main goal of this transmission is to provide faster gear shifts. Sequential transmissions are installed in motorcycles as well. They use this system because it provides ease of use for the rider.

The main difference in the sequential transmission is the gear pattern. A normal manual transmission moves in an H-pattern. But, to shift gears in a sequential transmission, the gear lever should be moved forwards and backward. This is similar to paddle-shift mechanisms found in automatic vehicles.

Another difference in this transmission is the clutch situation. In a traditional manual, the clutch pedal should be pressed to change gears. However, this is not the case with a sequential manual transmission. The driver can simply shift gears without worrying about the clutch. But, the gears can only be selected in the pre-defined pattern. This means that there is no skipping between the gears.

We hope that you understood the basics of this transmission. With that, let us move to the next section. There, we will take a look at some of the benefits offered by sequential manual transmissions.

Benefits Of A Sequential Transmission

A variety of vehicles use sequential transmissions, ranging from racing cars to sports cars. There are a number of reasons for this. Here, we will go through some of them in detail.

Sequential Transmission Benefit #1 – Faster Gear Shifts

Undoubtedly, the biggest benefit of a sequential manual transmission is the faster gear shifts it offers. Normally, it takes at least a couple of seconds to shift gears in a manual vehicle. It also involves a number of steps. The first step is depressing the clutch pedal. Then, the gear lever is moved to the desired position. Finally, the clutch pedal should be released. Although this is a simple method, the time it takes is not acceptable in motor racing scenarios.

In contrast, sequential gear shifts are done in an instant. The driver can quickly move through the gears by pushing or pulling the gear lever as intended. A paddle shifter can be used for this task as well. With the use of a sequential manual transmission, gear shifts only take a matter of milliseconds. This can be the factor that separates a race victory from a loss.

Sequential Transmission Benefit #2 – Weight

When compared with traditional transmission systems, sequential transmissions often weigh less. In the motorsport world, weight is one of the areas which receive the most attention. Race teams are always on the lookout for new lightweight technologies. The lightweight nature of sequential transmissions has made them popular among motorsport circles due to this reason.


The main reason for this weight advantage is the fewer number of components in the sequential transmission. This is especially true when compared with dual-clutch transmissions. This weight advantage translates to greater track performance. Also, the sequential transmission does not take much space inside the vehicle cabin, which is not the case with other transmissions. This also leads to weight savings.

Sequential Transmission Benefit #3 – Consistency

These sequential transmissions are more consistent than other types of transmissions. We mention this factor due to a number of reasons. With an H-pattern transmission, the driver has to think of the gear pattern before shifting. This is not the case with a sequential shift. Here, the gear shift only takes the push of the lever. Also, the same hand motion is used for each gear shift. As a result, a sequential transmission can consistently deliver fast gear shifts.

Also, in an H-pattern transmission, the hand position changes with each gear. This also requires some thinking from the driver. What you should understand is that each of these thoughts takes a few moments to get processed in our brains. And on the race track, victory is decided by these milliseconds. In a sequential transmission, the hand stays in the same position for each gear shift. This can gain a performance benefit for the drivers, which can hand them the victory.

Another term that is associated with sequential transmissions is “dog box”. I know what you are thinking. No, this is not related to our furry friends. Instead, this term refers to a technology used in these sequential transmissions. We will tell you everything about these dog gears in the next section.

Dog Box Transmission

Dog box transmissions also called ‘dog gears’ in short, are used in sequential transmissions instead of synchromesh rings. They get this name because of the large teeth they have which some people have compared to the teeth of dogs.

The dog clutch is a name used to refer to the clutch engagement action of these transmissions. It functions in a different manner when compared to traditional H-pattern transmissions. A traditional clutch uses friction disks to engage gears. But, in a dog clutch system, interference is used to achieve the gear engagement instead.

Using interference, two shafts are rotated, which enables gear shifts. As we mentioned earlier, this enables dog box transmissions to go through clutchless gear shifts. This is made possible because dog box transmissions require only a short period without torque transmission through it.

But, a dog box transmission can’t function on its own. For that, it needs the help of some other components. In the next section of the article, we will tell you about these components.

Components Of A Sequential Transmission

A sequential transmission is a bit more complex than a traditional manual or automatic transmission. As a result of this, it uses a number of different parts for its functionality. Most of these parts are not common in road cards. With that, let’s take a look at each of these interesting components.

1. Gear Selector Fork

All transmission systems come with a gear selector fork. This component is responsible for engaging the dog clutch. The dog clutch of the sequential transmission rotates with the output shaft. The gear selector force is what engages this to the gear which is rotating with the input shaft of the engine. In essence, the gear selector fork enables the driver to change gears by pushing the transmission into them.

2. Selector Shaft

All the gear selector forks of the sequential transmission are connected to the selector shaft. The selector shaft is usually made out of aluminum. This shaft contains several grooves cut into its surface. You may wonder what these grooves are for? Well, these grooves are followed by the selector pin, which is the component we will discuss next.

3. Selector Pin

The selector pin is located on the gear selector fork. The purpose of the selector pin is to guide the selector through the grooves cut into the selector shaft. Faulty gear selector pins can result in problems with the gear shift.

4. Multi-Plate Clutch

Normal road cars with an H-pattern shifter only have a single clutch plate. However, this is not the case with a sequential transmission. These transmissions contain more than two clutch plates. These multiple clutch plates are used for the connection between the transmission input shaft and the engine itself.

When a gear change is going to take place, the multi-plate clutch disconnects the engine torque from the input shaft. After completing the gear shift, the torque is re-connected to the transmission.

5. Sequential Gear Selector

The sequential gear selector is the component of the transmission that is responsible for rotating the selector shaft. Not only that, when the driver of the vehicle wants to change gear, this is the component that receives the input. The sequential gear selector can take many forms, varying from a traditional gear stick to paddle shifters behind the steering wheel.

These are the main components of a sequential transmission. Having a good understanding of these components is important for readers who are interested in installing a system like this in their vehicles.

6 Speed Sequential Transmission

Most sequential transmissions on the current market have six speeds. This means that they have a total of six forward gears that a driver can choose from. These six-speed transmissions often have closer gear ratios, which allows the vehicle to stay within the recommended rpm range of the engine. Sequential transmissions also allow the driver to quickly go through these gears really quicks, which is not the case with H-pattern transmissions.

Another transmission technology that has gained popularity in recent years is dual-clutch transmissions. These transmission systems called DCT for short, also have some similarities to sequential transmissions. Let’s take a look at these DCT systems in the next section.

Dual Clutch Transmissions

Dual-clutch transmissions combine features of a manual transmission with those of an automatic. Gear shifting in a dual-clutch transmission is done through the use of paddle shifters. These paddle shifters are often located behind the steering with, within easy reach of the driver. This allows the dual-clutch transmission to achieve gear shift times similar to those of a sequential transmission.

There are two clutches in a dual-clutch transmission. However, in vehicles with DCTs, there is no clutch pedal at all. Instead, the engagement of these two clutch pedals is completely automatic. These are controlled through electronic means, so they are capable of shifting gears without any driver input.

The operation of a dual-clutch transmission is even more complex than that of a sequential transmission. Here, the two clutches operate the odd and even gears separately. This means 1st, 3rd, and 5th gears are handled by one clutch, while the other clutch takes care of 2nd, 4th and 6th.

sequential transmission

This results in instantaneous gear shifts, along with smooth power delivery. These systems also have two input shafts, compared to the single input shaft used in sequential transmissions. This gives dual-clutch transmissions the ability to pre-select gears, unlike the liner gear selection process of the sequential transmission.

Now that you know about dual-clutch transmissions as well, we believe it is better to compare them with sequential transmission systems. That way, you can easily identify the advantages and disadvantages one has over the other, and make the best possible selection when purchasing a transmission.

Dual Clutch Transmission VS Sequential Transmission

These two types of transmissions are designed for two entirely different use cases. Sequential transmissions are mainly focused on racing and are not recommended for normal road use. Dual-clutch transmissions on the other hand have been developed to cater to a wide user base. They are designed to be comfortable, quiet, and smooth while also offering performance when needed.

When we take a look at the mechanical side of things, we can observe some differences as well. Sequential transmissions use a multi-clutch system, where dual-clutch transmissions have two separate clutch plates. The sequential transmission also uses dog gears, along with a single input shaft.

Dog gears are not used in a DCT, and they make use of two input shafts instead of one. Sequential transmissions are also lighter than dual-clutch systems. This makes them the best choice for motor racing and performance. However, their cost is also high when compared to that of a DCT.

All in all, we can see that the sequential transmission is the better choice for people who are going after the ultimate performance. However, it loses out on the usability front of the dual-clutch transmission. With that, we can understand that sequential transmissions are best suited for the race track, and the dual-clutch transmission is the best for road use.

Sequential Transmission Price

If you are interested in a sequential transmission, you should be concerned about the price. As we said earlier, these transmissions are expensive compared to traditional manual systems. The price of the transmission can vary depending on the make and model of your vehicle. Typically, the cost of a sequential transmission exceeds $2000. This is just the purchase cost of the system. After adding in the installation and maintenance costs, the total cost of a sequential transmission can be close to $10000.

This ties into the next topic of our discussion. In the next section of this article, we are going to tell you about a few disadvantages of sequential transmission systems.

Disadvantages Of Sequential Transmission Systems

Although a sequential transmission has a lot of benefits, there are some disadvantages to them as well.


As we mentioned before, the cost of a sequential transmission is extremely high. This can sometimes even exceed the cost of the entire vehicle. Because these transmissions are designed for ultimate performance, they use a lot of expensive parts. All these lead up to the cost of a sequential transmission being astronomical.


Sequential transmissions are designed to be used on the race track. As a result, they are very loud. The dog clutch is the main source of this noise. Most people will find this annoying and disturbing. This extremely loud nature is another factor that makes sequential transmissions unsuitable for road use.


Racing components are designed to achieve the best possible performance. Because of that, they are highly strained during use. The same applies to sequential transmission systems. These transmissions require to be rebuilt just after a few thousand miles. This extremely short lifespan is another disadvantage of sequential transmissions.

BMW Sequential Transmission

BMW is one of the most innovative automobile manufacturers on the planet. This was proven once again in 1996 when they introduced the SMG transmission system. SMG stands for Sequential Manual Gearbox, and it was first offered with the BMW M3. The transmission was an instant success, accounting for half of BMW M3 sales of that generation.

sequential transmission

The SMG transmission presented the driver with a number of selectable gear modes. These included six sequential manual gear modes along with five automatic modes. These modes were developed to be suitable for various road conditions that the vehicle may encounter.

For example, mode A1 was for situations where traction was low. The sequential gear modes, on the other hand, presented the drivers with the opportunity to sequentially shift through the gears to their liking. Gear shifts could be achieved by pulling on the paddle shifters or moving the gear lever back and forth.

STI Sequential Transmission

The Subaru STI is one of the most popular JDM tuner cars around. As a result, many companies develop sequential transmission systems for this model. A sequential transmission allows the drivers to get the most use out of the powerful boxer engine and the four-wheel-drive system of the Subaru STI.

One of the best STI sequential transmissions is made by X-Shift Gearboxes. They make a number of these systems. The Subaru +plus is a 6-speed sequential gearbox made by this company. This sequential transmission is rated to handle up to 1200Nm of torque, and has broken a speed record at 361.3 Kmph. It is made out of lightweight, aircraft-grade aluminum components. Not only that, the selector rods and selector forks have been made out of high-quality billed steel.

Facts about Sequential Transmission:

  1. A sequential transmission works the same way as a manual gearbox, but externally, it doesn’t move through an H-pattern, but only moves forward and backward.
  2. Sequential manual transmissions don’t use the clutch pedal during shifting and have dog gears instead of synchromesh rings in conventional manuals.
  3. The driver pulls or pushes the shifter to rotate the selector shaft to shift into the next gear in a sequential shifter.
  4. Sequential transmissions are faster than DCTs, and professional drivers can shift faster than a professional-shifted manual.
  5. Sequential gearboxes are significantly lighter and often more compact, and their dog gears sap less power than synchromesh ones.
  6. Racing vehicles, including NASCAR’s Next Gen racer and rally cars, commonly use sequential transmissions.
  7. Some aftermarket companies offer conversion kits and/or ready-built units for street-legal cars, but dog gears are less smooth and wear out faster than synchromesh ones.
  8. Racing sequential transmissions need a rebuild after just a few thousand miles, and sequential transmissions cannot skip gears like conventional manuals.
  9. Automakers occasionally offered sequential transmissions in their street-going cars, but they are not as common due to dog gears’ drawbacks.
  10. For those who want to drive a car with a manual gearbox, a conventional manual is still the best option over a sequential transmission for road cars.

Conclusion For Sequential Transmission

In this article, we discussed a lot of facts about sequential transmissions with you. We took a look at the inner workings of these complex systems and discussed some of the benefits on offer. Then, a comparison between sequential transmissions and dual-clutch transmissions was made.

Another factor that was discussed was the components of a sequential transmission. Not only that, but we also went over the price as well as disadvantages of this transmission system. In the final sections, we discussed the sequential transmission implementations by Subaru and BMW.

FAQS On Sequential Transmission

Here are some popular FAQs:

What Is A Sequential Transmission

A sequential transmission is a type of transmission used in race cars. It allows drivers to rapidly upshift and downshift through the gears. However, the gears must be selected in order, which means that drivers cannot jump between gears. Clutchless gearshifts are also made possible by these sequential transmission systems. However, the clutch still has to be used when moving from a standing start or when shifting into reverse.

How Does A Sequential Transmission Work

Sequential transmissions work with the use of dog clutches. These clutches do not use friction disks like a normal transmission. Instead,  they use two selector shafts. Because of this reason, the clutch is not needed in sequential transmissions. To engage the dog clutches, selector forks are used. These forks have selector pins mounted on top of them,  which move along the grooves of the selector shaft. The selector forks are mounted to the selector shaft. These move along the grooves of the selector shaft, engaging the gears in the process. The selector shaft is connected to the gear selector inside the cabin of the vehicle.

Are All Motorcycles Manual

Most modern motorcycles are manual and have a sequential transmission. Here, the gear shifts are done by the foot of the driver. Unlike sequential transmissions in cars, the clutch lever has to be pulled for each gear shift of a motorcycle.

What Is A Gearbox

The gearbox is one of the most important parts of a vehicle. The function of a gearbox is to change the RPM of a motor. There are several types of gearboxes. Some of the most common ones are automatic gearboxes and manual gearboxes.

Are Nascars Manual

Nascars have a sequential manual transmission, which allows the drivers to shift gears without using the clutch pedal.

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