Today, I drove about 90 miles with most it being at 60 mph. Half way into the trip I started to feel the steering wheel and what I think is the left front end shaking. The shake is bad enough that my wife even noticed it. The shake is not that bad until 50 mph plus. Yes, my tires are old and worn. I can't believe this event is tires since the issue popped up rather quickly. How do I go about troubleshooting this. With smaller vehicles, I could normally feel wheel bearing or ball joint issues. Being a 3500 4x4 I doubt I can feel anything by just moving the wheel/tire. Thanks, for any help you can give.