Steering, and bucking?? HELP

Okay so my steering wheel makes a humming noise when I steer. It is most noticeble at slower speeds. I just got 4 new tires on the car. Also, now when we are driving the car seems to skip...or slightly buck....more so feels like a skip. What could these mean? I really need help as I am mechanically declined! thanks

regarding your steering, your power steering fluid needs to be replaced. I use Mobil 1 Synthetic ATF. it has solved the whining noise when I turn the van.

Regarding the 2nd question about shifting, I'll let my other better informed and experienced forumers answer that.