Death wobble?

I own a 99 jeep cherokee that is lifted w 3in coils and a.c.o.s @ 1 1/2 totalled at about 4.5 inches of lift. im using rustys lower control arms and rustys track bar w/frame mount. and skyjacker steering stabilizer. p285/75r16 m/t tires mount on 1 1/2 inch wheel spacers from spyder tracks one of which the lug mount is loose in the front penger side. Whenever i hit a bump in the road at speeds like 40, or 60 the entire front axle will shimmy violantly. i cant figure out why this happens.. sure is scary. any ideas