You cannot 'wind rear lock on' It's a myth.
Unlocked = open = no voltage input, it has a slight bias to the rear but it's certainly not 2wd. It's unpredictable, bordering on dangerously unstable on anything prior to 2005.
'Wound on' it's locked at 50/50, like a 4WD axle winding, plow steering Hilux.

Buy a Neetronics Callum, they work. In fact, if you set it up properly it'll be almost as good as a non DCCD gearbox!