trans. not shifting in a 89 Ranger

[Ken N.]

My son has an 89 Ranger 2.3. Will not move if put in over drive but if you put it into drive it will go but not shift unless you pull it down into 2nd. And if you try to pull back in to drive it acts as if its in netural. He tried changing the vacume modle and does same thing. and suggestions

Thanks Ken N.