Yup, you are correct. US spec VX's were 4hi and 4lo only while JDM's had 2hi also. I'm guessing your problem is mechanical in that you aren't able to shift the transfer into 2hi. If you are in neutral and the truck is stopped, you should be able to make the transition. Sometimes the t-case can be a little stubborn when it comes to shifting and a little finesse is necessary to make the shift. I've had the same problem with Fords sometimes being obstinate...