I searched through 12 pages here and couldn't find any answers to my problem so maybe this is a new one. I have a 2006 XLT and I have recently been having problems with the four wheel drive. It will engage perfectly whether stopped or at speed. But, when rolling at speed and I turn the knob to disengage from 4H to 2H it stays in for a little while then comes out with a hard bump. It feels like the bump is in the front end but I am not sure. It seems as though it will disengage perfectly if sitting still but will not when rolling. Also it will occasionally fly out of four wheel, while the knob is still in 4H position, with a loud bump then reingage while rolling. Anyone have an idea what it might be?