1998 suspension

i just replaced ball joints and had an alignment. everything was fine until i hit a bump going 60. all of a sudden the whole vehicle started shaking and i had to come to a complete stop for it to stop. i took it back to the alignment place and they checked to make sure everything was tight. they couldnt find anything loose. well it still does it. does anyone know what i may have done wrong when i replaced the ball joints? i have triple checked everything. i dont know what is causing this. please help

Check the tie rod ends. The procedure to properly check tie rod ends on that vehicle id to grab hold of the tie rod end near the knuckle and pull hard on it. Side-to-side shaking does not reveal play on those.

There are 4 to check. The outers, you pull down, and the inners you pull toward the front of the vehicle.