I purchased a used JK with a Teraflex 2.5 lift with springs and shocks verified by Teraflex with 35's Nitto Grappler installed. I've tried a few things to solve the handling issue and now I believe it may need adjustable control arms to add positive caster to help the drive-ability. Have I read correctly that the stock upper control arms will give no more than +4.5 caster angle? Everything I have read states I need about +6 to 7 degrees of Caster to solve this dartiness or flightiness handling. Can I only change the uppers arms to achieve this 6/7 caster setting? The writeup I found here at the Project-JK only talks about adjusting the upper control arms. My 14 year old wants this Jeep when he turns 16, but if I can't get it to drive any better, then that will never happen.

 

You can just get uppers( they're a bit cheaper than lowers) but lowers allow for more adjustability. I have Teraflex lowers on mine and it handles great at 6.5 degrees of castor.