The used car dealer had replacedYou probably have resolved your issue, but thought I’d share my experiences. Bought a used 2017 JKU. It has a lift of approx 4” with 35” tires. Driving was a little like playing Russian Roulette. Swaying badly at high speeds, taking corners at higher speeds were nail biting events, and I had pops and groans at slow speeds. Steering input was constant. Here’s what was done to resolve my issues…
1. Ball joints and tie rods replaced and aligned. Helped some, but not completely.
2. Trailing arms for front were installed. They enabled a better alignment, but I still wasn’t happy with the results.
3. Drag link was terrible. Got an expensive one ($300) from Metalcloak. It was adjustable, and well worth the money. Installed it and the drive was way worse. Adjusted it a bit (takes 2 minutes) and it was a HUGE difference. Much better. Had it realigned for good measure.
4. Lastly, I put new rear sway bar end links on. The old one was rusted and the boots were completely rotted. It didn’t make a difference in driving quality, but the drag link had already improved the ride 100%.
5. Another thing I learned, and you should remember this when you increase tire size, is that the computer thinks you have 32” tires. When sizing up, you need to recalibrate the computer. Mine had not been and my transmission was taking a beating and my speedometer was 7-8 mph off. I bought a dongle and an app (total of $60) and recalibrated myself. Instantly fixed my shifting issues.
I was told by 3 mechanics that “it’s just a Jeep thing.” Whenever I hear that, I realize I’m talking to an idiot.
Ball joints
Tie rod ends
Drag link
I took it back last week for power door lock after the part came in. They checked the alignment and looked it over at the 4x4 shop next door. Their mechanic said the ball joints need to wear in. That was contrary to what I had read here from others. Maybe it will get better.
Still scary to drive at 60 to 65 mph. I believe the rubicons come stock with 33" tires, which is what I have. The speedometer seems to be accurate.
Not giving up on finding out what it is. Will be taking a closer look this weekend. If it is a Jeep thing driving like this, they shouldn't be street legal.