Tech Article Title Author Date
Electronic Differential Lock (EDL/EDS) AudiWorld 1996

Electronic differential lock, or EDS (german acronym for same), is not a differential lock as per usual. It uses the ABS sensors at driven wheels (i.e. left/right front on FWD, left/right front and left/right rear on quattro), to determine if one of the two wheels is spinning faster than the other. At some speed differential (approximately 25 mph / 40 km/h), the highly sophisticated fifth-generation ABS/EBV actually pulsates the brake momentarily at the spinning wheel, effectively transferring the torque through the open differential to the wheel with more traction. This system is effective, but due to the stress that it would create on the braking system, it is only used up to speeds of about 25 mph / 40km/h.

One can really hear/feel it work on front-drive models, as it makes the typical ABS type pulsating sound when activated during wheelspin. On quattros, I find it harder to notice, as even on snow/ice the car seems to spread the power to wherever the grip is with the Torsen and the EDS so quickly that the time that it is activated is too short to really hear.

The system is simple yet effective, causes no substantial loss off power transmission, and after 25 mph / 40km/h, one has the benefit of ASR on FWD models, or the security of quattro.