99 4runner front end problem

I have a 99 4runner limited 4wd. At around 50 to 60 miles per hour I get a
violent shaking that pulls my steering wheel back and forth and is even more
pronounced when I press the brakes. I had the tires balanced and rotated
first and the brakes look and feel fine. Theres no play in the rotors when
I took off the tires. I can also drive the truck on surface streets up to
40ish mph with no vibration whatsoever. What are some potential solutions??
I feel like the wheels are coming off when it happens so I've avoided the
highway altogether.