My wife has a 2018 Jeep Wrangler JL with 40,000 miles, V6 and automatic. It is stock. I drove it the other day (I rarely drive this vehicle) and found the power steering acting oddly. She said it started doing this recently. At highway speeds the steering becomes very stiff, as if there is some kind of variable-power assist thing going on. At slower speeds it is normal.
I found this while changing lanes on a sweeping curve. It felt like the vehicle is resisting your command to turn the steering wheel.
Further it appears harder to turn at first and slightly easier as you force the wheel. It is not easy to diagnose while driving because you would need a wide-open space like the salt flats! Further, it is just not safe to crank the wheel at 60mph!
Is this normal??
Also, fluid level is between MIN and MAX and there are no leaks.
My brother has a 2018 Wrangler Unlimited and the steering is typical Jeep: constant wandering requiring constant correction.
I wouldn't say it is normal, but I wouldn't expect Jeep to tell you the issue either. If you know a good front end shop in your area, I would suggest letting them check it out to make sure everything is ok.
Since you checked fluid it's hydraulic rather than electrical power steering. I'd start by pressure-testing the pump.
https://www.youtube.com/watch?v=jB4cnhi1faY
I found a TSB and I am going to start with this. It is TSB-08-092-18; 'Low Steering Assist at Highway Speeds'.
Will need to call a dealer and figure out the next steps with them.