I drove my 4in lifted jeep for about a year with only transfercase drop. It didn't have vibes but I went through two sets of universal joints in the rear. I now have sye for a couple years and its much better on the u-joints. Though a buddy of mine had a four inch lift and the transfer case drop didn't get rid of his vibrations so he had to do the sye right away.
2002 Jeep Wrangler X
4" suspension lift/currie anti-rock
33" Mickey Thompson Baja MTZ
Front & Rear ARB plus 4.56 gear
Front & Rear Warn Bumper w/9.5ti on Front
Poison Spyder Rocker Guards