What is a Sequential Transmission?

What is a Sequential Transmission?

Sequential Transmission

If you’ve ever watched a bit of WRC over the last year or so, you may have noticed that the drivers are changing gears via a tall shifter next to the wheel – and if you’re wondering what on earth is going on, then get ready to learn about Sequential Transmissions.

While you won’t find one in many road cars unless modified, a sequential transmission is a fairly basic form of gearbox, one where, as a driver, you’re quite limited as to how you go through the ratios.

However, sequential transmissions do come with their advantages, and have deep roots in motorsport – let’s see what they’re all about.

How does a sequential transmission work?

The core ideal of a sequential transmission is that, at any one time, you either go up one gear or go down one gear – hence the ‘sequential’ element of its name – you cannot, for instance, go from third to fifth or fourth to second.

A sequential transmission is, on a technical level, a manual gearbox, albeit one that has some semi-automatic mannerisms in how you change gear, as you can either change with a proper sequential shifter or with electronically-operated paddles behind the steering wheel.

If using the stick-shift method, then pushing forward will move the gearbox up one gear, while pulling back will go down a ratio.

Don’t make the mistake that some hydraulic auto gearboxes are sequential transmissions, though, with the likes of Tiptronic and SportShift ‘boxes not being on the same mechanical level.

Do sequential transmissions have a clutch?

Technically yes, they do – however, the clutch in question is a ‘dog clutch’, which engages with gears via teeth (or ‘dogs’) instead of friction like a regular transmission would.

A dog clutch’s two rotating shafts are made so that one will push the other and so rotate at the same speed and not cause any slip.

That last point is what makes sequential transmissions so desirable in motorsports, as a dog clutch offers more control when going through gears as well as faster shifts, but also incurs less wear.

This makes them ideal for the performance demands of cars and bikes being pushed to their limits on track, and also offer affordability due to such durability. The new Rally1 cars in WRC, for instance, brought back the sequential transmission for that very reason.

However, the way in which a dog clutch works makes it not particularly useful in road cars where you want a smoother gear change, and not one that offers such an aggressive transition.

Which vehicles use a sequential transmission?

On the road, you’ll only really find that it is motorbikes that utilise a sequential transmission, with the rider typically shifting gears with their foot via a ‘one down five up’ six-speed gearbox.

However, it’s on the track where the sequential transmission is at its most prevalent.

The 1950s and ‘60s saw the slow rise of the sequential transmission in Grand Prix racing before evolving into what would become the early paddle-shift cars of the ‘90s.

The GT1 race cars of Le Mans in the mid-to-late ‘90s, including the famed McLaren F1 GTR, all made use of the sequential transmission type.

These days, you’ll find some form of the sequential transmission in the likes of WRC cars, NASCAR machines, and V8 Supercars.