Ed A. Stevens said:
DW and shimmy are encouraged by too much toe-in. Lift increases the toe-in with the inverted-Y steering system in an XJ. At a minimum, the toe-in needs to be adjusted after a lift is installed.
The drag of toe-in pulls the tires back and takes the slop out of any loose bushings or jointed connections (why we add toe-in, to keep the wheels straight under normal driving conditions, even with normal bushing & joint clearances). Excessive toe-in pulls more on the steering and knuckles, and the additional force can expose previously unknown excessive bushing clearances or slop.
Usually DW starts with a bump, and then accelerates through movement in the loose bushings (you will know if it's true DW).
Unbalanced tires are almost always found as part of the problem.
A loose track bar bushing/bolt at the axle is common major contributor (as is the frame end tie rod end or frame bracket, and the pittman arm tie rod end).
A loose shock bolt can exhibit shimmy (the verge of DW), as can almost any of the joints and bushings that make up the XJ front suspension.
The solution is alignment (starting with toe-in), find and correct the loose component, and then realignment (toe-in and caster) to determine the least amount of toe-in and the most caster (within reason: 0" to 1/8", and 2-8 degrees respectively) to provide the quality driving experience where you are most comfortable. More toe-in and more caster tend to allow the XJ to track straighter with less effort (they add self-centering force on the suspension), but these increased forces also tend to exploit any excuse to promote shimmy and death wobble (if you have a loose component it is more likely to cause a problem with more toe and caster).
HTH?
