WEll...since your sig says you're running 36's....

I'm going to say its one or more of the following:
1. lack of track bar with too much lift, frame goes one way, axle goes the other.
2. Play in the steering shaft
3. Play in the steering box
4. loose/worn pitman arm
5. loose/worn tie rod/drag link ends
6. bad ball joints
7. Very common-loose steering box, or it has pulled away from the frame
8. flex on frame from steering box....running 36's...tou should have a steering brace.

Thats all I can think of for now..

-remy