Xtrac shows seamless gearchange alternative to dual clutch transmission


December 1, 2010

Xtrac IGS is applicable to a two speed EV transmission

Xtrac IGS is applicable to a two speed EV transmission

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After two years secret development in motorsport competition, Xtrac unveiled an important new driveline technology this week in the form of an Instantaneous Gearchange System (IGS). It does exactly the same thing a dual clutch transmission achieves with less weight, cost, and complexity. The secret to Xtrac IGS is the integration of a ratchet and pawl mechanism between each gear hub and the main shaft so that two consecutive gear ratios can be selected and engaged simultaneously, but with only one set of gears driving.

Conventional gearboxes have always had some serious problems associated with needing to interrupt engine torque in order to change gear. Apart from increasing fuel usage, hydrocarbon and CO2 emissions, momentarily cutting power delivery to the rear wheels obviously also reduces performance.

Porsche was the first to develop an answer to this problem with its Doppelkupplungsgetriebe (dual clutch transmission - DCT) and the DCT is now in common usage in cars and has just been applied to motorcycles for the first time by Honda.

Size, weight and complexity are the main drawbacks of the DCT. Now motorsport transmission specialist Xtrac has applied its high performance engineering skills to design and develop a seamless gearchange known as IGS or Instantaneous Gearchange System. IGS is small, lightweight, and is now ready for commercial development in motorcycles, electric vehicles, cars, trucks and buses. IGS was unveiled this week in Berlin at the International CTI Symposium “Innovative Automotive Transmissions Hybrid & Electric Drives”.

The secret to Xtrac IGS is the integration of a ratchet and pawl mechanism between each gear hub and the main shaft so that two consecutive gear ratios can be selected and engaged simultaneously, but with only one set of gears driving.

“When introducing new technology to the automotive mainstream it’s important to have progressed beyond the initial research and development phase,” said Xtrac Technical Director Adrian Moore.

“Car makers like to see practical demonstrations to show that the technology actually works and is more than a concept. With our motorsport experience we have the advantage of two years of racing IGS with professional teams.”

IGS is protected by worldwide patents, and the company reports that initial development will focus on improving the efficiency of electric vehicle powertrains. Xtrac has considerable experience in the design and manufacture of transmission systems for experimental, prototype, pre-production and specialist low volume vehicles, and a study is already underway to implement IGS into a two-speed EV transmission with the aim of ensuring the optimum performance of the vehicle.

Xtrac is based in Berkshire, UK, with satellite motorsport operations in located at Indianapolis and North Carolina in the United States. Its gearboxes, differentials and driveline components are used in Formula One, IndyCar, Touring Car, Rallying, Rally Raid, GRAND-AM and Le Mans sportscar racing.

About the Author
Mike Hanlon Mike grew up thinking he would become a mathematician, accidentally started motorcycle racing, got a job writing road tests for a motorcycle magazine while at university, and became a writer. As a travelling photojournalist during his early career, his work was published in a dozen languages across 20+ countries. He went on to edit or manage over 50 print publications, with target audiences ranging from pensioners to plumbers, many different sports, many car and motorcycle magazines, with many more in the fields of communication - narrow subject magazines on topics such as advertising, marketing, visual communications, design, presentation and direct marketing. Then came the internet and Mike managed internet projects for Australia's largest multimedia company, (Australia's largest Telco), (Australia's largest employment site),,, and a dozen other internet start-ups before founding Gizmag in 2002. Now he writes and thinks. All articles by Mike Hanlon

Looks fine, solving the inertia issues of the lagre spreads of EV ratios.

Needed for my Famiglietta concept MPV/stationcars at : .

Søren Algreen-ussing

Nice article but Porsche was not the first to develop a twin-clutch transmission. Howard Hobbs was the first to develop and produce the Mecha-Matic twin-clutch transmission. The transmission was used in a few British cars in the 1950\'s as well as being raced in a Lotus Elite sportscar by the inventor\'s son David Hobbs.


No It wasn\'t Howard Hobbs either. Adolphe Kégresse developed DCT first for Citroen in 1930s but they abandoned the project.

Facebook User

still stuck in the last century with gearboxes for electric vehicles. In wheel electric motors need no external gearbox. Check out and this is 2 or 3 years old.


Do a Google for preselector gearbox or transmission. They\'ve been around for decades. They\'re very popular in drag racing.

Facebook User

Thanks for the mentioning Mr. Kegresse\'s transmission. Oddly enough, my second edition copy of \"Modern Transmission Systems\", by Arthur Judge (1969) makes NO mention of Mr. Kegresse!!


Look at where the book is published. Initial credit usually goes to the countrymen of the respective publisher. People still credit Marconi with the Radio but it has been overturned in 1943 to Tesla. ( The same can be said about the \'inventor\' of Carbon Fibers. Swan vs. Edison depending on who is writing the history books.

Chang Liu
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