Steering Wheel Vibrate problems of the 1997 Infiniti QX4

The contact owns a 1997 Infiniti Qx4. The contact stated that when the vehicle was traveling 50 mph or more and it hit a bump, the steering became unstable. The steering wheel began to shake and the contact felt as if he would lose control. The contact replaced the struts and shocks twice and had the lower tie rod, tire and steering rack replaced. The failure continued. The failure mileage was 150,000 and the current mileage was 210,000.