WRC Drivetrain


Citroen C4 WRC

I found this article few years ago by accident during my everyday browsing and I save it in my comp. I find it interesting and I want to share it with you. I sand a mail to webmaster to ask him for permission, but I have no answer to my mail. So, if he is not available, I will publish it, but with some of pictures from my arhive...
Enjoy reading!


Symmetrical All Whee Drive drivetrain of Subaru Inpreza 2007
Symmetrical All Wheel Drive drivetrain of Subaru Inpreza 2007


The Subaru Impreza S13's drive train in numbers

Where far more than expected meets the eye, we look at the complexities of the gearboxes and differentials used in the Impreza WRC2007, and what goes into making them work: The Subaru World Rally Team has produced over 100 WRC gearboxes since 1999. Almost 50 WRC differentials have been built since 2004.

Subaru Impreza WRC sequential gearbox
Subaru Impreza WRC sequential gearbox


Each gearbox takes 85 hours to build and costs 100,000 $. Coupled with the rear differential the transmission system contains over 700 individual components. Each differential takes 16 hours to build, and costs 30,000$. The front and rear differentials share components to reduce costs, whereas the centre differential is unique.

Subaru Impreza WRC Gearbox
Subaru Impreza WRC Gearbox


Once a gearbox has been built, it takes three hours for the team's dedicated dyno to run through the complete test procedure before it is used on a rally.
There are two special insulation panels fitted to the side of the gearbox to shield it from the heat of the exhaust which runs alongside it. Each plate is made from titanium and ceramic coated, using a process designed for space craft.
The engine, gearbox and differential are all individually oil sealed, meaning that each can be removed and replaced without fluid loss.
The gearbox lubrication system has a capacity of 4.5l and is fitted with a high-flow oil pump to keep temperatures down. The gear shift system operates at a pressure of 150bar, or 2,500psi for almost instantaneous shifts.
Each unit uses over 40 specialized oil line connectors. Approximately half of these are built specifically for the Subaru World Rally Team, and all use aircraft grade materials.

Subaru Impreza WRC Gearbox with differential
Subaru Impreza WRC Gearbox with differential


The gear shifter retains the road car's H pattern but uses a hydraulically and electronically controlled semi-automatic gear change system to shift each gear in fewer than 0.1 seconds.

Undergoing 3500 gear shifts on every rally, each unit is rebuilt after approximately 750km of competitive use or two rallies. The oil is changed for every rally.
The gearbox and differential run at 100 degrees Celsius, and need their own oil coolers to maintain that temperature. On hot rallies such as Greece, the operating temperatures can reach 120 degrees Celsius.

Subaru impreza WRX differential, sti spec C
Subaru impreza WRX differential, sti spec C

It takes between 10 - 12 minutes to replace a gearbox and rear differential. The fastest time on a rally was 10mins and 20 seconds set during Rally Deutschland 2007.
The housings of both units are cast from magnesium for strength and to reduce weight. A gearbox weights 95kg when wet (full of oil) and a differential 25kg wet.



Subaru Impreza WRC Flywheel ProLite advanced racing clutch

Subaru Impreza WRC Flywheel ProLite advanced racing clutch



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Books to read


Some useful links:

- f1technical.net, a great site with a lot of technical information’s and explanations. Site is updated daily with news from F1 word.

 - autosport.com, This site is a legend. A bible for racing lovers. News from all around the word. Unfortunately, to get access to all news, interviews and to open the site completely you should be subscribed to Autosport magazine. Anyway, great read.

James Allen on F1
- JA.F1 site (or blog) ovned by ITV Sport’s lead commentator on Formula 1 James Allen

Joe Saward blog
- joesaward is the Joe Saward official blog about Formula 1 world. Joe is an journalist, who write primarily about politics in and around motorsport, specifically on the FIA Formula 1 World Championship

Vital F1
 - vitalf1.com/ is another great site for Motor Sports fan’s like me. Site is relatively new, but great fun, with great discussion forum, Formula 1 news and forum.

 GP update
- f1.gpupdate.net, Site with fresh news from Formula 1

Planet F1
 - planetf1, another site with many different articles, news and statistics. Biased toward British teams, but anyway good read.

Gurney flap
 - gurneyflap.com, Great history site. You can learn a lot from this site. Pictures, cars and many many more. Great.

4ormula1 is a database of Formula 1 history and statistics of drivers, teams, grand prix, and all results since 1950.

Missed Apex Podcast
Enjoy range of Podcasts and Articles on Motorsport. Every week a Formula one chat on Missed Apex F1 Podcast with F1 journalist Joe Saward and tech Analyst Matthew Somerfield as guests. Also the exciting all electric racing series formula E on eRadio Show and Bike Show Lean Angle Podcast.

Racecar engineering
-Racecar Engineering, an online magazine with a lot to learn from, a lot of technical information’s and explanations

 - fia.com, La Fédération Internationale de l'Automobile, representing the interests of motoring organisations and motor car users. Head organisation and ruler in auto sport.

 - wikipedia.org, I don’t believe that I have to tell you anything about this site. It’s not about Formula 1 technology, but you can learn a lot about that too.

Sutton Images

grandprix photo

 - carbibles.com, a great site for normal car users. Here you can find explanations of almost everything about your car and how it works. Technical reviews and explanations of some in-car gadgets.

Dare To Be Different
- Daretobedifferent.org Susie Wolff and UK governing body of UK motorsport have joined forces to launch Dare To Be Different, a high-profile new initiative which is about increasing female participation, not just on the track but in all aspects of the sport.

Giorgio Piola web site