The Effect of Various Limited-Slip Differentials in Front-Wheel Drive Vehicles on Handling and Traction

Speed-sensing Limited-Slip Differentials (LSD) such as Viscous Couplings (VC) are becoming major players in Front-Wheel Drive (FWD) applications. Traction Control Systems (TCS) which control the wheel slip by influencing the engine torque output and/or actuating the brakes are also introduced to the FWD market in growing numbers. A few applications for torque-sensing LSD's have recently entered the market. All of these devices are known mainly for their traction improvements. However, all systems have demonstrated that they also positively influence handling and stability even under normal driving conditions.

This paper presents a series of proving ground tests which investigate the effects of speed-sensing and torque-sensing LSD's as well as TCS on traction, vehicle stability, handling and torque-steer. Factors affecting torque-steer are described and key vehicle design parameters are identified which greatly influence both the application and compatibility of LSD with FWD.

Test results show the differences of these devices concerning their traction improvement capability and their influences on acceleration, throttle-off manoeuvres, braking and self-steering behaviour during cornering. The paper also reports results concerning the compatibility of these LSD's with Antilock Braking Systems (ABS). It is also shown how LSD and TCS complement each other when combined in a vehicle.