Read up on this helpful information if you haven't already:
http://www.kevinsoffroad.com/how-to-fix-your-own-death-wobble/Trackbar is usually first culprit: Check tie rod end, bushing on other end, and any slop in the bolt (no warped bolt hole etc)
Next I'd look at tie rod ends in the steering system (drag link, and tie rod).
If those are all good, time to look at ball joints, wheel hub/bearings, and control arm bushings.
Death wobble can be a tiresome trouble to track down... personally I'm tired of running my front wheels toe'd-out as a band-aid fix, so I'm replacing all of the above parts with custom designed and built parts. When in doubt, break out the welder! Haha