I had both tie rod ends shot. It was pretty serious, no alignment or diff. tires could stop it. Most likely that's your problem too, the faster I went, the less I felt it. Mostly when driving straight. There is so much play now that the tires just go wherever they want until the play restricts it. You might not be able to just jank on the tire and think you'll know. The local tire store put my car up on the lift and had a movable plate that was air actuated under both front tires. It moved rapidly from side to side. That's when you can see the real play.