Had same exact problem on my old YJ. It ended up being the shaft that connects the steering column to the steering box. The u-joints were dry and binding. Replaced it with a new one from quadra-tec.
If you take the shaft out and move the u-joints by hand, it will be very obvious if they are bad
“He who knows not and knows not that he knows not, he is a fool, shun him.
He who knows not and knows he knows not, he is simple, teach him.
He who knows and knows not he knows, he is asleep, wake him.
But he who knows, and knows he knows, he is wise, follow him.”
89 yj 4 banger 5sp. 2" BL 31x10.50 fixed up and sold
97 tj 4.0 Auto 4"RC lift 33x12.50 mud rovers on outlaw IIs . Smitty bumpers