2008 Ford F-450

Steering problem
2008 Ford F-450 V8 Four Wheel Drive Automatic 58000 miles

My 2008 F450 4x4 diesel dually has an issue
with the way it tracks down the road.
I had new tires installed and the alignment done
about a month ago- and now when I go down the
highway it seems to have a mind of its own! It seems to vier right and left and it has some play in the wheel of about 2 inches also? The Ford dealer replaced a wheel bearing and checked alignment and said it was fixed- but it still does it! I feel it is unsafe!
Could it be a steering box going out? All tie rod ends and suspension looks tight- everything is always greased like ball joints? HELP ANY IDEAS?
July 14, 2010.

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