If you look at the Haldex 4 unit ,and it has the ELSD option it will have a module with two hydraulic pipes running from the pump assembly, to the rear of the unit . With ELSD it looks like this ,, The unit with an ELSD has a second wire runing to a fluid solonid valve that does not exsit on a Unit without that option this valve takes presure from the pump and applys to one side or other of a piston in the ElSD unit to force torque transfer bias to the Right or Left Rear Wheels on command there is an extra clutch pack on the side of the haldex unit that the axel passes through the Elsd computer can send hydraulic presure to one side or the other dynamicly altering the torque going to each rear wheel ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_Jt3uyyQnNw.html . if you enable sport mode with awd it will dynamicly shift the torque to outside rear wheel when you corner , "if one rear wheel ends up on a slipery surface instead of using the brakes it will vector the torque to the rear wheel with grip this is a lot more efficent then applying the brakes on wheel with less grip to force the torque to the other wheel..
You know who has really really really good four-wheel drive systems that could sleep on Jaguar X-Type it was partner made by Ford but they have the only four wheel drive system that is true 60 40 power 60% power to the rear 40% power to the front one of the best four-wheel drive systems I've ever used and it's better than Audi's Quattro it's just a shame that it didn't come in supercharged or turbocharged that would have been very interesting I drove in through snowdrifts that wrx's couldn't get through and I was the only one with PennDOT plow trucks with your state plow trucks on the road they looked at me like I was crazy
