Here's some more good info and an explaination of ADC.
http://www.youtube.com/watch?v=D3yfPVT5nSI
My 2005 does not have the 4X4 & 4X4ADC positions - just 4X4.
The tire situation is more important than this guy explains. Obviously all of the manufacturers design their suspensions with the machine's unsprung weight being an important factor.
So when the cheap factory tires need replacing and you move up to a tire with more plies and some stiffness you add weight to the suspension it doesn't have figured in the design.