Originally posted by dark_rex
split hairs all you like, when a wheel slips on a quattro equipped audi (that's not more than 5 years old ) rather than just redistribute the power to a gripping wheel, the wheel is braked electronically through the ABS system. this equates to a NET LOSS of power, rather than a simple redistribution of 100% of the power.
In 1998, Audi began employing the Haldex electro-hydraulic clutch. this also works by taking power away from spinning wheels rather than reditributing power to gain the best ratio for each wheel.
EDL was offered initially in '94 by Audi.
Haldex is only offered on the TT Audi's lineup. The rest of Audi's lineup uses Torsen. My '99 A4 2.8 quattro did NOT have EDL. With that said, I do believe it was not purely mechanical. I think the front and rear diffs were open and it used the ABS in some form to limit wheelslip. I could be wrong however.