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Sequential Transmissions
Clutchless Shifting
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Sequential Transmissions
If you love being able to control your car in your own way but you don’t want to go without the convenience of an automatic, why not find a happy medium?
A sequential transmission gives you exactly that. In this article, we demystify the technology and tell you the pros and cons of this type of gearbox.
What is a sequential transmission?
First of all, the term ‘sequential gearbox’ tends to be used inconsistently. Fundamentally, it only refers to the actual process of shifting: you have to shift each gear up or down in sequence – you can’t jump from second to fourth for example. But the term is also used to mean a transmission that’s a cross between manual and automatic.
Unlike manual shifting, you change gear in a linear sequence. So you can only ever go up or down one gear. However, the process is largely automated: all you have to do is touch the lever. That’s why the sequential shifting system is often referred to as semi-automatic. But ... in today’s sports cars, that’s not entirely accurate. For example, at the red light they go straight from fifth to first, which contradicts the usual definition of a sequential transmission.
Since you can’t skip a gear, your freedom is somewhat limited. But you do get more of a feel for the car and for driving. One big advantage of a semi-automatic is that there’s no torque converter, which means your fuel consumption is lower. When it comes to gears, a fully automatic shifting system is obviously far more convenient because there’s no clutch. But no clutch also means no influence. So a sequential transmission gives you the best of both worlds.
Which makes of car have a sequential transmission?
Major manufacturers have different names for a sequential transmission (in both the original and colloquial sense), including:
- SMG (BMW)
- R Tronic (as in the Audi R8)
- Smart
Porsche GT3 CUP (six-speed claw transmission)
Sequential transmissions in motorsport engineering
The technology behind sequential transmissions originates in motorsport. No doubt you’re familiar with the unmistakeable earsplitting sound a sequential transmission makes – like a wheezing crackle. The reason it’s so loud is because of the straight cut (spur) gears. But the types used in Formula 1 and the like are the deluxe version, because the priorities are very different to those for road driving. Race cars usually have a rocker switch on the steering wheel, whereas normal cars have a gear lever. Either way, shift command transmission is exclusively electrical.
Semi-automatics change gear incredibly fast on account of the special clutch design (and dual clutch transmissions are faster still). Race cars sometimes even have triple clutches. Cars for road use have helical (bevel) gears and draw-key gears, where a cone/wedge presses balls between the main shaft and the gears in order to change gear.
On a sequential transmission as opposed to a manual one, traction interruption is minimal, which is a big advantage. But the gears are under much more stress, which means they wear faster. This is irrelevant in motorsport where the transmission only has to deliver top performance once, and can then be replaced. As a sequential transmission has no torque converter, it also saves you fuel.
Sequential transmissions in sports cars usually have their own oil circuit with an electric oil pump. This ensures that a consistent pressure of 40 to 50 bar is maintained for shifting. The clutch is hydraulic instead of manual, and a second valve block controls the gear change.
How to handle a sequential transmission
Quick but calm – in this video, our colleague JP explains how to avoid snapping your gear lever and what double-clutching is all about:
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Comments
PS Automobile GmbH
20.02.2024, 17:14 Uhr
Hallo
Wir würden gerne ein Porsche 964 Getriebe G 50 / 6o auf Halobautomatik umbauen lassen
Bitte kurze Info, wir benötigen 12 Satz pro Jahr
Azezz
10.05.2023, 22:49 Uhr
Is the sequential transmission installed on all cars?
Azezz
10.05.2023, 22:49 Uhr
Is the sequential transmission installed on all cars?
David
24.05.2023, 14:51 Uhr
Kann man mit einem sequentiellen Getriebe auch voll automatisch fahren? Ähnlich der Fahrstufe D bei einem Automatikgetriebe oder muss ich immer selbst das Schaltpaddel bedienen?
Jerome
18.04.2024, 13:29 Uhr
Hallo David,
ein sequentielles Getriebe wie es genannt wird, kann theoretisch über eine entsprechende Elektronik ähnlich wie ein AT Getriebe geschaltet werden. Allerdings würde das die Vorteile dessen mehr oder weniger nicht erreichen können.
Sequentielles schalten bietet folgende Vorteile:
Ein Gang wird nach dem anderen eingelegt, direkte Sprünge von z.b.: 1in4 oder 6in3 etc. sind nicht möglich.
Die Schaltbetätigung kann durch einen elektrischen Aktuator, oder mechanisch erfolgen.
Kürzere Schaltzeiten, welche durch Schaltautomat noch kürzer werden können.
Simplere Technik
Nicht zu vergessen, ein sequentielles Getriebe braucht auch eine entsprechende Wartung. Da ist es nicht mit einem Ölwechsel getan.
Mfg
Franke, Klaus
02.04.2023, 17:24 Uhr
Bei meinem KFZ, BMW 530d, Touring, Baujahr 2005, ist das SMG - Getrieb mit der Fahrstufenbeleuchtung komplett ausgefallen. Das Fahrzeug ist knapp 200.000 km gelaufen. Keine Geräusche, Ölverlust e.t.c. vorhanden. Könnt ihr helfen?
Robin
16.05.2024, 14:09 Uhr
Hallo Klaus, wir haben uns auf Fahrzeuge des VAG Konzerns spezialisiert und können dir daher leider nicht helfen. Am besten suchst du eine Werkstatt auf die sich auf Fahrzeuge von BMW spezialisiert hat.
Juho
31.05.2023, 10:07 Uhr
Hello
I needed H-pattern gearbox change sequenthial gearshift system.
My car is Subaru Impreza wrx sti year 2015, do you have these car sequenthial shifter?
Br,
Juho
His first car was a Polo Mk1 with a 40 Weber twin carburetor and 129 PS (95 kW). His second was an Audi 50. Today Bartek tunes Lamborghinis to 1000 PS (735 kW). Even as a young boy, Bartek disassembled vehicles and put everything back together better. He wrote his high school diploma with oil on his fingers. The trained automotive mechanic with a focus on engines and gearboxes was determined to go into motorsports. In his 10 years in Formal 1, he supervised 73 races, including as engine mechanic for Ralf Schumacher at Toyota. Since 2010, he has dedicated himself fully to his company BAR-TEK® and helps his customers to bring VW and Audi engines to peak performance.
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