I have developed a noise (click/clunk??) in the front wheels when the drive is engaged. More noticeable when turning the wheels at very low speed. No noise at all with front wheels disengaged. Truck has about 94,000 on it and has spent most of it's winter months in Florida so front wheel drive has been rarely used. Moved back to Pa. this past winter but didn't notice any problem until last week when the front was engaged to get through some mud. Now it's there every time I engage the front. What could be causing it?

 

sounds like your stub axle u joints. Did mine a couple of times.

 

X2^^^ You will probably notice some rust just below the caps or even slop in the joint when you rock it back and forth. Check the wheel bearings and ball joints at the same time, there is a good chance they could be bad as well. There is a good write up here somewhere on ball joint replacement which will cover u-joints, ball joints and bearings if I remember right.