and despite all the literature slippage is at least partially required in all systems for them to react.
No, it isn’t.
Ok which one doesn't? Once you do a deep dive on both Subaru and Audi mentions once it detects "variation in wheel speeds", ie. slippage it responds by adjusting the torque distribution. Do you see different?
ps. The Honda magic rear diff is quite incredible.
What's your definition of slip n grip? To me, it's 2wd (e.g. fwd) until slip is detected, then power is distributed to other axle (e.g. rear wheels). That is not what's happening with Subaru's system. There's always power to all 4 wheels. Torque just gets distributed based on grip. Mainstream automatic cars default to 60f/40r but can lock clutch packs to get up to 50/50. Manual cars are 50:50 with a center viscous LSD. My STI has a planetary center diff that defaults at 41f/59r and can be incrementally locked manually or automatically up to 50/50, Torsten diff in the rear, helical LSD in the front, plus brake torque vectoring based off throttle, steering input, wheel speed sensors, etc.
There is power supplied to the front/rear in a 60/40 default. Once the power gets to the rear it flows through a torsen limited slip differential which in order to send power to the wheel with grip one wheel needs to slip. Therefore their system requires slippage to REACT to conditions which has been my point all along.
Subarus own spiel:
I also included an explanation of how a torsen differential works (which is by slippage) :
But, if a Torsen differential is used in this case, as soon as the slippery wheel starts to spin excessively, the speed change will be transferred to the corresponding worm wheel. The right worm wheel transfers the speed change to the left worm wheel, since they are connected through spur gears. Here comes the tricky part! The left side worm wheel will not be able to turn the corresponding worm gear, because, as we said, a worm wheel cannot drive a worm gear! As a result, the whole mechanism gets locked, and the left and right wheels turn together.