Haldex is an electronic slip and grip system, especially the older generations.. If the clutch can't lock up to any degree, then it can't transfer power. The newer generation take in a lot more data from sensors to "anticipate" slip and then tell the coupling to start locking up. Unfortunately, Haldex requires frequent fluid changes of its wet clutch, and requires additional maintenance of the pump, such as cleaning the pump screen of clutch particles.Ford Focus RS used the dual electronic Haldex setup as well. IMO those aren’t true AWD systems like we’ve been otherwise discussing, since if you burn up a Haldex there will be exactly 0% power going to that wheel regardless of conditions, at least how Ford explained it.
In a viscous coupling, instead of an electronic controlled lock up clutch, the silicone fluid mechanical properties does the lockup within the clutch
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