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In the Spotlight Technical

Sequential gearbox transmissions … the basics

Going back only a few years it would have been seen as total overkill for an off-roading competition 4×4 to have a short stick shift sequential gearbox. How times change … now it is the gearbox of choice for many.
So how does a sequential box improve performance over a conventional box, you may ask. Well it’s all about speed shifting.
The driver may only ever select the next-lower or next-higher gear ratio, basically, all in line with shifting simply up or down passing through neutral to reverse at the lower end of the range.
These are known as sequential transmissions. If you have ridded a motorcycle, then you have operated a sequential gearbox, this is where this type of transmission is most commonly found.
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The Advantages
  • The sequential shift is quicker. For example, to go from 2nd to 3rd gear on the “H” pattern, you have to push the lever up, over and up again. That takes time. On a sequential gearbox, you simply push the lever up for every gear change.

 

  • The sequential shift is consistent. You do not have to think, “Let’s see, I’m in second gear so I have to go up-over-up to get to third.” You simply push the lever forward — it’s the same motion for every gear.

 

  • The hand location is consistent. With the “H” pattern, the location of the shift lever changes, so you have to think about where to put your hand depending on which gear you are in. With a sequential gearbox, the shift lever is always in the same place for the next shift. The sequential shift has no surprises. If you mis-shift with the “H” pattern in a race (for example, down-shifting to 2nd when you meant to go to 4th), it is possible to blow up the engine. That can never happen with a sequential gearbox.
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Sequential transmissions often incorporate a synchro-less dog-clutch engagement mechanism (instead of the synchromesh dog clutch common on H-pattern automotive transmissions), in which case the clutch is only necessary when selecting first or reverse gear from neutral, and most gear changes can be performed without clutch use. However, sequential shifting and synchro-less engagement are not inherently linked, though they often occur together due to the environments in which these transmissions are used, such as racing cars and motorcycles.
Sequential transmissions are generally controlled by a forward & backward lever, foot pedal, or a set of paddles mounted behind the steering wheel.
In some cases, these are connected mechanically to the transmission. However in many modern examples, these controls are attached to sensors which instruct a transmission computer to perform a gear shift, many of these later systems can be switched to an automatic mode, where the computer controls the timing of the gear shifting, much like a fully automatic gearbox.

 

Check out this sequential tutorial video …

 

MTI Racings take on their new sequential gearbox …

 

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