dailynewsnblog
What’s the diff?
Audi
An actuator, overdrive gears, and a differential combine to intelligently transfer torque between the rear wheels. They do so almost fully variably depending on the driving situation and ensure Agility and Stability.
Audi
Audi
A look at the assembled differential.
Audi
Audi
An illustration showing how torque is controlled across the rear axle.
Audi
A look at the assembled differential.
Audi
An illustration showing how torque is controlled across the rear axle.
Audi
Like all performance Audis, the RS5 uses Quattro all-wheel drive, here with a limited-slip center differential that splits power between 70/30 and 15/85 front to rear.
We have enjoyed torque-vectoring rear differentials on previous Audi RS models—the ability to send more power to individual rear wheels as necessary has played a big part in why people like cars like the RS3, TT-RS, R8, and so on. In those cars, the rear differential uses a clutch for each wheel to achieve that, but for the new RS5, Audi Sport decided to develop something new, internally.
It’s calling the new setup Dynamic Torque Control, and it does away with hydraulic clutches in favor of an 8 kW, 40 Nm electric motor (also powered by the 400 V traction battery) and some planetary gears. The electric motor lives on one side of the axle and applies torque to a powered sun gear at the other side. This sun gear acts on planetary gears, then a fixed sun gear connected to an open differential. It can add or subtract torque from the ring gear to the half shaft for an up to 1,475 lb-ft (2,000 Nm) split across the axle, or send it back to the open differential for a straight 50:50 split. Because it’s controlled by the electric motor, the diff will react in just 15 milliseconds, making the car neutral or allowing it to oversteer depending on the drive mode.
Split personalities
Tobias Sagmeister/Audi
The handling can be neutral, or oversteer-y.
Tobias Sagmeister/Audi
Tobias Sagmeister/Audi
It helps when you don’t have to pay for your own tires.
Tobias Sagmeister/Audi
Tobias Sagmeister/Audi
The RS5 was very easy to slide and catch.
Tobias Sagmeister/Audi
It helps when you don’t have to pay for your own tires.
Tobias Sagmeister/Audi
The RS5 was very easy to slide and catch.
Tobias Sagmeister/Audi
Driven on the road in Balanced, Comfort, or even Dynamic, you might not ever notice how clever the torque distribution is at the rear. The weather was fairly atrocious for much of my road driving in the RS5, with a mix of rain and late May snow at altitude. Yet despite wearing wide summer tires on 21-inch wheels and all that power and torque, its behavior was never anything less than locked down and stable on the road. So this really is a true all-weather performance car, in the way the best fast Audis always are.
