Didn't know where to post this but I found this web site by accident and was very impressed with the explanation related to 4Motion, 4XMotion and locking / limited slip Touareg differentials.
http://blogs.youwheel.com/2015/02/14/volkswagen-touareg-4motion-awd-system-comprehensive-review/
http://blogs.youwheel.com/2015/02/14/volkswagen-touareg-4motion-awd-system-comprehensive-review/