AWESOMATIX supply as on optional item a ball diff. In principal the diff operates like common ball diffs that were standard items for many years, prior to the new trend of gear diffs, in all touring cars.
They operate by having two metal plates pressing against each other having hardened steel or ceramic balls in between.
This ball diff is a bit different as it also incorporates a fully sealed housing in which oil of different grades (cst) can be inserted in order to achieve different levels of resistance, thus being able to fine tune it in a similar way as a gear diff.
The diff when completely assembled gives exceptionally smooth feel without a hint of slipping. According to other users' experience the ball diff may give better traction on certain conditions, such as low traction.
I might be able to test this weekend and will report back.