Probably some sort of balance issue. First suspect is tires, less common is drive shafts. HAVE IT CHECKED FOR A WORN OR LEAKING STEERING DAMPER
Go to a tire shop and see if your tires are balanced correctly, if your tires are out of balance they could cause vibrations at highway speeds.
If you are in Full time it is recommended not to go over 25mph that is probly why it shakes put it in part time you can go up to 55 mph in part time
check and replace tires and tie rod ends as neccassary
my jeep was doing this and they told me all this stuff that could be wrong with it and i got my tires rotated and it fixed the problem..
You should have the wheel alignment checked. Could be a $20 Fix.
because Jeep Wranglers are easy to flip, especially turning at high speeds.
A shake that is that speed sensitive is usually a bent rim, or bad tire.
It would be 55 MPH.
Flat out on a level road with a good wind behind you, probably 55 mph.
55 mph = 88.51392 kph
55 mph * 1.6 = 88 kmph
first check the front end steering. idler arm is usually the culprit.