GKN Driveline, famed for its ubiquitous constant velocity joints, has extended its product capability to the car industry following the development of a range of class-leading, all-wheel-drive technology systems. The latest example to be revealed is the compact Fiat Panda 4x4 due to reach the UK market in early Spring, 2005.
Fiat has broadened the appeal of its diminutive Car of the Year 2004 winner by introducing an all-wheel-drive option engineered in partnership with GKN Driveline. Even before its launch, the car has been greeted internally and externally as a major success.
To secure such an important Fiat contract, GKN Driveline’s design team had first to compete with the world’s leading transmissions suppliers. At stake was not just a major components supply opportunity, but also the responsibility of managing the engineering development programme on behalf of the client.
Fiat’s brief was to endow the Panda with traction capability to tackle challenging winter roads, but to achieve this with minimal compromise to the car’s refinement and having the least impact on both technical complication and cost. GKN Driveline met this challenge by developing a simple but effective 4x4 installation comprising a front power transfer unit (PTU), a two- piece propshaft a viscous coupling in front of the rear differential, a rear differential module (RDM) as well as front and rear sideshafts. GKN Driveline supplies all these components, partnering Getrag for the PTU and Dana for the RDM respectively.
The key to the system’s efficiency is the viscous coupling. On a homogeneous grip road surface, where there is negligible front wheelspin, the front and rear wheels rotate at almost the same speed. As a result the viscous coupling, which provides a locking action proportional to the difference in speed between its input and output shafts, directs only a small proportion of engine torque to the rear wheels. On mixed-grip surfaces the front wheelspin can increase, causing the viscous coupling to pass more torque to the rear wheels, apportioning torque delivery according to the available grip at either end of the car.
In addition to its simplicity, this arrangement has many other advantages. The system is entirely automatic, requiring no input from the driver; it is entirely mechanical, requiring no electronic control; it has a benign impact on driving dynamics; and it provides good compatibility with anti-lock braking and stability control systems – a key requirement of any modern 4x4 transmission.
GKN Driveline’s meticulous design and careful selection of joints for the sideshafts and propshaft also ensure that the NVH (noise, vibration and harshness) penalty is minimised, despite a significant increase in the number of driveline components compared to two-wheel-drive models.
The extensive research and development effort undertaken for Fiat on the management of the Panda’s 4x4 development places GKN Driveline in a strong position to extend its engineering and supply service to car makers in this growing market sector. With a variety of all-wheel-drive systems available including the most sophisticated intelligent 4x4 traction control applications, GKN Driveline has much to offer vehicle manufacturers world-wide.
GKN Driveline is one of the world’s leading suppliers of vehicle driveline products and systems commanding 42 per cent share of the market for constant velocity jointed (CVJ) sideshafts. The company is a global enterprise, headquartered in the United Kingdom. It recorded total sales of £1.9 billion in 2003. The company currently has 21,000 people working at 49 locations in 31 countries.Published 20 October 2004