The US transfer and the VTD transfer valve assembles are different. The US valve applies full line pressure to the transfer clutch, as the normal, turning the C solenoid on, turns the transfer pressure off.
The VTD valve assemble is the opposite. It has no applied pressure to the Limited Slip clutch, as the normal. Turning the C solenoid on, turns the transfer pressure on.
I don't know why this is so, it may have something to do with the way they are to 'fail safe'. The US fails to full AWD, the VTD fails to no Limited Slip clutch, as it always has AWD.
The difference, I believe, is the way the transfer spool valve is machined. Being the easiest and cheapest way to change the action in production. The two have different part Nos.
If it is right, and I won't know for sure, till see the spool valve out of a US transfer unit, it means there is a way to fit the JDM VTD box to the US car and have it operate off the US TCU, by swapping the VTD transfer assemble, for a US transfer valve assemble.
Harvey.
