If the TOD system is working as it should at a stop there should be no power going to the front wheels (I know, DUH!). When you start to move there should be no power to the front wheels until about 10-15 mph. At that point you should see the first light on the front wheels light up on the TOD display. There really isn't any way to tell if there is actually power going to the front wheels though. I can never feel the shift in power during normal dry driving. The only way to make sure that the TOD works is to get the rear wheels to slip a little (maybe that snow storm you were talking about). Find a patch of ice/mud/slick road and step on the gas. If the TOD is working correctly you should see all three of the lights on the front wheels of the TOD display light up and you should feel the front end grab. You might also hear the transfer case whine a little. The power shift should only last a split second unless the rear wheels start to slip again, at which point the TOD will throw power to the front wheels again.
When I first got my VX I thought that as the rear wheels started to slip that the TOD would throw power to the front wheels and leave it there. That isn't the case. It sends power forward in short bursts. Just enough to stop the rear wheels from slipping and then it pulls the power back. I live in Colorado and I love the TOD in the winter. As others slip and slide as they take off from a light I can just stomp on it and the TOD takes care of the rest; pulsing power to the front wheels as it's needed.
To be safe, I would also shift the VX into 4 wheel low to make sure that everything works with that too. That won't tell you if the TOD system works, but it will tell you if the four wheel drive system works and that the transfer case is working.
Good luck and keep asking as many questions as you need to.
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