Design News for Mechanical and Design Engineers

Known as Cross Wheel Drive (XWD), the new system is said to offer capabilities that aren’t available on conventional all-wheel drive products. In addition to providing a variable torque split between the left and right sides of the car, XWD can optimize traction when a vehicle takes off from a traffic light, even in dry conditions.

“The beauty of this system is that it does more than transfer torque from the front to the back,” said Steven Shannon, president and chief operating officer of Saab Automobile USA. “It transfers torque from side to side. And with Cross Wheel Drive, zero-to-sixty is going to be faster.”

Cross Wheel Drive accomplishes that by reading electronic inputs, including those from accelerometers, wheel speed sensors, yaw sensors, steering wheel angle sensors and throttle position sensors. During hard acceleration from a traffic light, for example, XWD’s sensors “know” the vehicle’s weight is moving backward, and therefore shift traction to the back of the car.

“It reads the throttle setting and decides, ‘The driver just put his foot to the floor,’” Shannon said. “Then it changes the power distribution.”

Along with inputs from the sensors, XWD incorporates a power takeoff unit in the front, prop shaft, rear drive module and an electronically controlled limited slip differential. All the hardware components were built by Swedish automotive supplier, Haldex. 

The technology will reach the American market in April, when it appears on the Saab 9-3 and the Saab Turbo X, before eventually filtering through the rest of the company’s product line.

	Saab's Cross Wheel Drive system allows variable torque split between left and right sides of car.