I believe you, a couple weeks before this happened I did about 1200 miles disconnected at about 35 psi and the truck was as smooth as i could have wanted the whole time. something has changed but according to two shops and my impact everything was and is tight.
I have a 2020 JT Gladiator. I had a 2010 2Door JK Sport before that and a number of other CJs before that. The death wobble is new to the JK/JL/JT, I do believe but am not sure. It was never an issue with the CJ's which was my last Jeep before the JK. I had the wobble in the 2010 JK and put a single after market dampener on it. Fixed the problem. Drove it 200K after that and never a wobble.
If everything checks out correctly - tires, torque specs on all arms, end links, etc..... then, I would increase the caster slightly on the front end. Turn the front lower control arms a half turn counter-clockwise (make them longer), and turn the front upper control arms half turn clockwise (make them shorter). Try that for a while. It should feel better. If you think you may need more, go a half turn more.
Also, as tires get bigger, this little nuance may matter more. Mounting Your Tires | Yokohama Tire . It explains the red and yellow dots. Could be straws on a camel's back. I put a 2" leveling spacer on my 3" Mopar/Fox kit and gave myself the wobbles. Between 42 and 45mph you feel the steering getting light, and the right bump or divit in the road will send my front end into seizures. Even my dual stabilizers cannot "stabilize" it. I'm aware of/use to it from my 2010 JK but someone on here says it can happen with any of the solid axel Jeeps. Also what a lot of literature says. I'm wondering if stiffer springs might tighten things up in front because of this 2011 article Death Wobble cured after 4 years and 49,000 miles - JeepForum.com . I am concerned that there is too much soft between the FOX shocks and the springs which are slightly progressive (one twist spiral at the top). There's some of my thoughts, for what its worth.
The steering box may be a stretch but if there is play in the box, couldn't that contribute? Jeep is replacing my steering box and reprogramming some-related-thing for free. Physics, geometry, fluid dynamics, engineering, not my thing for sure. I got the soft spring idea from this article, Death Wobble cured after 4 years and 49,000 miles - JeepForum.com . Then thinking about my JT, my springs are soft and I think the FOX shocks that came with the kit may also not be that firm. My JT rides great, that's just how my thinking was going.
Sloppy steering and play in the steering wheel is totally different than Death Wobble. You can't keep driving when you got death wobble, you got to come to a complete stop and then hope you can still drive once you start moving again, feels like the whole vehicles coming apart. Springs, Steering Boxes, Steering Stabilizers aren't going to cause these things, it's almost 100% of the time something loose, tire wear, ball joints wore out, track bar bushings worn, tie rod bushings worn, or caster issues. Never ever have I heard of soft springs being the issue, I would think stiffer springs would not absorb as much harshness of the road and cause it over soft springs. Still never heard of springs being a direct cause and you mask the issue many ways, dual stabilizers, better stabilizer, but eventually it's gonna happen again when that stabilizer wears out prematurely.
