Truck Gearbox Insight with Stefan Honens
Truck racing is a unique form of motorsport, one that pushes development into a distinctive avenue, resulting in solutions specifically developed for the discipline. These are unique parameters which are largely not common in other forms of racing.
Gearboxes are definitely one such aspect.
“Gearboxes are based on standard units and because of high torque, we use big gearboxes,” says Stefan Honens, Technical Director at Team Tankpool24 Racing.
“The regulations for truck racing describe what kind of gearbox we can use. They say that it has to come from an ordinary, road-going truck.
“When it’s a 16-speed box, we need to have 16 gears, but in racing we only need seventh and eighth gear, the two top gears,” he continues, shedding some light on the unique specifics of gearboxes used in truck racing.
Despite the trucks being equipped with a manual transmission that has more gears than other race cars, there’s relatively little work to be done with the gearstick for the drivers.” explains Honens.
“In the braking zone, most of the time you shift down, in mid-corner you accelerate and then you shift up as soon as possible and use the engine torque to come out of the corner.
“At the Nürburgring we have 10 gear shifts per lap, five up, five down. Places like the Red Bull Ring – no shifts. It’s all about shifting times, you need to shift as quickly as possible
Shifting technique is, however, determined by the engine characteristics.
“If you have a powerful engine, you don’t shift,” he says.
“Sometimes you do it to help the rear stepping out. Some drivers use the downshift and play with the clutch to get the rear to step out and then they turn the truck before the corner. They have a straight exit and can accelerate in the straight line, being able to use the full engine torque and full traction.
The speed limit also plays a role when it comes to gearboxes. Top speed is limited [to 100mph] so ratios are chosen depending on the engine torque.
Despite the fact that gearboxes are based on road-going units, they’re far from components that can be bought off the shelf.
“It’s all based on standard components but they mixed up from different boxes and all put together into what is sort of a racing box. We can use different internal components if they’re commercially available,” says Honens.
Gearboxes are an area where teams do their best to make a difference. “We try to reduce friction with oil. Everybody has their own philosophy,” adds Honens.
And what about that all-important component reliability?
“Normally the gearboxes don’t fail, because you can predict it. Sometimes we find out that the gearbox will go soon and we have to change it, it takes around 20 minutes.”
If you have ever seen the size of the ‘boxes then this fact is yet another to wonder at in the amazing world of the FIA ETRC!