How about this perspective:
Under normal conditions the front and back plates of the VC are rotating at
the same speed. The back plates being driven by the motor/rear wheels, the
front plates driven by the front tyres.
With the front DS disconnected the front plates will not turn at all. The
faster the van goes, the greater the speed differential between the front and
rear plates, the greater the heat build up. Finally the VC either melts or
explodes .

Corollary: We go to great lengths to ensure a <5% diference btwn. front and
rear rolling radii. Disconnecting the DS leads to a major violation of this
rule.

JoE.   -- not a mechanical engineer and I don't even play one on TV.