[fredjacksonsan]

Which 4 wheel drive system do you have? If it is a part time system, this sounds like you were in 4 wheel drive on pavement. On the GC the manual states that you must torque and untorque the driveline a couple of times to insure disengagement. In mine, I get a clunk when it comes back to 2wd, and sometimes it takes being in 1st gear and giving it gas and letting off a couple of times for it to disengage. Make sure when doing this you are on a slippery (as in dirt, grass, etc) and moving in a straight line.