I had 2014 Jeep JKU - completely stock, and I installed a 3 inch lift kit and 35 inch tires roughly 700 miles ago.

Since then, the Jeep shakes at highway speed and sometimes during sudden acceleration.

I have replaced all control arms to adjustable ones from Clayton.
I have front and rear adjustable track bars.
I also balanced tires twice since and got the Jeep aligned although the shop said there wasn’t anything they could have done because I already aligned it pretty good?



Because I installed the lift kit and tires at the same time, I have no idea what is causing this vibration issue.

Maybe I should try balancing tires again?
DS went bad all of a sudden after lifting it?

Does anyone have any advice or tips on how to diagnose it or approach this issue?

 

Where the tires balanced on a Road Force machine? It puts pressure on the tire as it is spinning. It would detect an out-of-round tire/wheel combination.

What size wheel are you running? 35's on stock wheels are doable, but can exhibit strange vibrations since the too-narrow rim can cause a bit of side-to-side motion in the tire.

Did you check all of your suspension joints? A bad ball joint, drag link, track bar, or tie rod might start showing up as vibrations.

Are your driveshafts stock? The stock driveshaft cv joints don't like much lift, especially the front. A bad CV joint will cause the symptoms you are experiencing. A switch to an aftermarket u-joint driveshaft isn't that bad, except you need to watch out for the pinion preload crush sleeve. There are videos on how to get the pinion nut back on without affecting preload. I've used the "fish scale" method myself with success.

If you don't mind a little low-speed vibration sometimes when first starting out after being parked for a while, you might want to ditch the wheel weights and go to good quality balance beads. I recently switched and am very impressed how well they work. Don't' often get the low-speed vibration unless I start out slow and stay slow for a while. Other than that, smooth as silk!

 

Your caster on that alignment is pretty high, which is opposite of most people's issues. That factory front axle has a built in caster of 4.2°, and you are at 5.6°, which means your pinion is actually pointing downward by 1.4°, which would be pretty rough on a factory driveshaft that is now having to deal with increased separation from the transfer case by 3". If you remove the front driveshaft, how does the jeep drive?

Most of us lifted folks would run caster in that 4-5° range. there's no exact science really to perfect caster, it's more a range. you're really wanting to achieve acceptable steering without going to high that you introduce driveline vibes.