Mychailo,
Further research reveals that with the DCCD disconnected, it defaults to a 34:66 drive ratio. That tells me that the diff isn't open? If it was open, it might be 100:0 or 34:66 or even 50:50 depending on what it felt.
So I think it might not be viscous, but it certainly has the potentially to be able to be run without the DCCD controller
It also seems that this system was designed for rallying. My previous comments about wanting it to disengage when you pull on the handbrake - turns out it does this!!
This link (may require rego) has a scan of the manual relevant:
http://www.clubsub.org.nz/forums/vie...highlight=dccd
Cheers,
MAtt