About control arm
 

I'm having to replace the upper control arms on my 07 JK to adjustable ones so I can tilt the pinion due to a vibration after changing the driveshaft. My question is, do i need to change out the lower control arms as well before i tilt it? Sorry if this sounds dumb but i'm trying to learn all this stuff as i go.

If just take advantage of north ridge sale and get RK lower and upper.

No you do not have to get lowers. Many of the manufacturers kits only offer upper or lower control arms, mainly for adjusting the pinion angle and caster.

I think most would recommend lower over upper. How much lift?

6 in the front and 4.5 in the rear

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6" lift, what size of tires you running, must be massive!

With 6" of lift you should replace all eight stock arms with adjustable arms and front axle housing with the C's positioned to get caster back.

6" lift with all stock control arms? it is likely that the driveline vibe is going to be the least of your worries. Once you minimize your pinion angle you could be into the - caster range which means on road handling may be dangerous. Are the springs bowed as well. Do you have the stock front axle housing?

In all honesty I don't think anything other then cut and reweld Cs and springs seats is gonna fix your problems.

Agreed, and going to a longer arm would help too. If I were skimping I would want the front lowers and rear uppers for pinion angle adjustments. But again, with this much lift you really should consider lengthening the arms.

If you are planning on changing the rear uppers I would highly recommend going with the RK uppers and lowers. This will push your rear axle back up to 1" to recenter your wheel in the wheel well. It will also allow you to adjust your pinion and thrust angle.

However at 6" of lift you will benefit from a long arm set up. I am surprised you didn't have a driveline vibe even before the driveshafts were installed.

PM us if you would like to talk in more detail on this.