Development of an Electronically-Controlled, Limited-Slip Differential (eLSD) for FWD Applications

Limited-slip differentials improve traction and handling when compared to open differentials, but offer no active modulation and can compromise typical driving. A number of passive control systems exist that attempt to reduce this compromise. Electronically controlled limited-slip differentials (eLSD) are being introduced that allow active control of the differential in all driving situations and can be operated as an open differential, a fully locked differential, or at any point between these extremes.

Such an eLSD system was implemented in two General Motors front wheel drive cars-one on an automatic transmission and applied by the transmission pump, the other on a manual transmission and applied by an external pump. This eLSD system contains a multi-plate wet clutch connected to the differential carrier and right side half-shaft of an all wheel drive capable transmission. It was a bolt-on unit, mounted to the right of the transmission output of a multi-axis transmission, replacing the intermediate shaft.

The eLSD system, its implementation, and its effects on traction and handling are detailed. The effects of adding the eLSD system to the demands on the automatic transmission hydraulics and oil management are also discussed.