My 2001 ford van f350 6.8 liter, has a shaking in front end and it pulls to driver's side, what could that be?

The drivers side tire is worn on the inside with threads showing.

Have the front end checked, including the alignment.

Sounds like a bad tie rod end. If you drive on that too long, you'll kill the ball joints.

Replace the tire, and have your local mechanic perform a tire rotation. That shall fix the pull.