One place to look is the driveshaft carrier bearing (the driveshaft is too pieces, this is the bearing between the two halves). They are prone to going out with lifted vehicles; but that doesn't mean it couldn't go out on a non-lifted truck as well. Check for some side-to-side/up/down slop in that bearing.

[edit] Just re-read that you said front of vehicle. The above would be for noise/shaking from the rear of the truck. You don't have a front brake caliper dragging, do you?

Sean Strawmyer
Back and ready to rock...... crawl.

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