2018 JK 2-door sport Auto lifted 2.5" on 35's (how original), stock control arms and driveshaft. I geared myself to 4.56 and installed Truetracs in both the front D30 and rear D44. Lift, gears and tires installed around 10k. Jeep currently has 17k and I've been trying to find the cause of a shutter that shakes the jeep and makes clunking noises upon coasting anytime below 30mph. Sometimes it happens, sometimes it doesn't. Started happening around 15k

I thought I messed up the gear install so I pulled the carriers and checked specs, pinion was still within spec, B/L was good, carriers were still in nice and tight. Thought it might have been rear axle bearings. Replaced both sides. I pulled the front axle shafts to isolate it to the rear. Still there. My next thought is to pull the rear DS and give it a whirl around town in front wheel drive. The only other thing I can think of is if my rear TT is messed up. Any further ideas?

 

Pull the rear driveshaft and see it it is it. I doubt it is the cause though. How are your tires? Track bars tight? Pinion bearing preload?

 

Tires were purchased new at the time of install. Along with the lift, I installed some adjustable trackbars. Both ends were checked when I pulled the carriers. Yes, the rear pinion preload was still good. When I say it shakes the Jeep, I mean it rocks it side to side yet on one occasion, I viewed the left rear tire and it showed no signs of axle side to side movement.

 

Here's a video. You can hear and see the camera shake a bit at the tail end of the video.

 

Thought I'd update. Turns out it's the driveshaft, specifically at the Rzeppa joint. This is just a 2" lift with about 7,000 miles on it since the lift.

 

Glad you figured it out! Our two doors are real finicky on the driveshafts after seemingly any lift... That's why I bit the bullet and ordered new front and rear 1310 units from Driveshaft Direct when I installed my lift and have not had any issues thereafter! That said, I have heard of some having good luck going with the high angle Rzeppa joints to solve this issue. I did not as I figured I would rather change a u-joint on the trail then trying to change out a Rzeppa joint! Good luck!