How about the inner tie rods?
I had a shakey steering the other day. Doing about 60, I thought the wheel was going to fall off, whatever caused it fixed it self in about 3 miles. I'm thinking a rock or something stuck in the treads.
I do have a slight shaking again, but I think my tires are out of balance and I know my wheels can't still be straight-love the potholes and manhole covers!
Also make sure your lugs and axle nuts are tight!