help steering feels very loose!?!?!?!?!

[71Seth]

I have a 97 4x4 1/2 ton. I bought the truck new and noticed a pull to the right. so i swaped the front tires from left to right. Pull go much better. Now i have bought 15x10 with 31-10.50. The pull is back again and as you turn right(Only right not left and not all the time), once the top of my steering wheel gets between 1 and 2 o'clock, the truck will turn alittle farther than i want it to on its own. Makes going around curves at highway speeds very scary at times. Also with the new wheels and tires i gained a pull to the left when braking. I have replace: left and right lower ball joints, idler arm, adn have pitman arm but it is not on yet. Checked upper ball joints, tie rod ends, and wheel bearings. all look good. Will try to get pitman arm on this week and get an alignment. Could it be the gear box leaking internally, or maybe the steering valve sticking????
Sorry for so long of a post, But i'm looking for help
Seth