hmm. does it do it while moving and turning? or only when stopped and trying to turn the wheels? is there any whining noises from the power steering pump when it does it?
My first thought is the steering u-joints on the front axle are bad. When they go bad it can feel like the jeep is in 4wd when turning. you can sometimes hear a clicking noise while turning when they are bad. One way to check them is, one at a time jack the front wheel off the ground. Turn the wheel to full lock, then get out and spin the wheel by hand. If it binds up while trying to spin it, you know u have a bad joint. If they are worn enough you can also grab them with your hand and see if the have slop in the joint.
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