While getting my Suburban ready for vacation last week, I took it in for a frontend alignment (was pulling to the right). The shop called me and said it need both bottom balljoints, idler arm, and new pitman arm. I told them to go ahead and do what's needed. It ended up being a 738 dollar bill. Should also note it has brand new tires on it as well. Went and picked it up last Saturday and immediately noticed steering wheel doesn't return to center. Also noticed the front wheels seemed like they were wandering while going down the road ( Sorry, that's the best way I know to describe it). We were leaving on Monday and the shop closed at noon, so we went ahead and loaded it. As soon as we got on interstate and got up to 70-75 mph I noticed it would weave from side to side after making a lane change. It wasn't just a little either, it would scare the holy crap outta you. After about 3 hours of driving I finally got the hang of it and it did okay. I let wife drive it and she pulled to side of interstate after about 15 minutes of fighting to keep it in one lane. Any ideas on what would cause it to weave so badly? I noticed they didn't change the caster adjustment. I've read that caster affects the steering wheel returning to center. It drove great before having work done. She was solid as a rock on interstate. Only problem was it pulling to the right. I apologize for the long post, but wanted to explain problem as best I could. I'm taking it back to shop Monday, just looking for ideas on what could be the problem. Thanks in advance.