I have a 3" lift on my XJ. I am going to add another 3". Do i have to change my trac bar, lower control arms or anything esle?

 

Yeah if you want it to drive properly.

With a 6 in lift i recommend a long arm kit.

You will also need a SYE if you havnt already gotten one for the 3 inches. Definitly think about regearing since you obviously will be going to a bigger tire. Once you go above 3 inches it gets expensive. I would invest in a 5 1/2 inch lift kit and just sell your 3 in kit it will have everything you need except for gears.