if i take a feed off the handbrake switch and take it to a relay using this as the coil wires then to the other connections break the black wire connecting the 4x4 ecu feed as you would when wiring the dash 2wd/4wd switch this should give the effect of cutting the visco drive when lifting the hand brake making handbraking possible without risk to your transfer box .
Does this sound right to any one if so ill give it a bash should make the long winter days more enjoyable
When the 4x4's were used by the Police, they were modified to operate a relay from the handbrake, as you suggest, but were wired into the two brake switches. Remembering that one breaks and one makes. The ECU will think the brakes have been applied normally and disconnect the transfer box. Just also remember that it will not disconnect below 16 mph.