3000 series 4wd is mechanically held on by a spring clutch until released by hydraulic pressure. So engine needs to be running and 17 Bar pressure applied by putting 12v on 4wd solenoid.
So it's just the opposite of the 6100 series then? Would the same principal not still apply though? In other words if it's disengaging 4wd with speed then check to see if the 4wd switch is sending signal to the relay to send power to the solenoid?