Hey Brian - I think the Needle Bearings are only about 15 bucks a piece......

I think the Hubs are quite a bit more...

yeah, if you are 2wd the bearings are cheap. unless really loose i would not assume intermittent vibrations. are you feeling it in the wheel or in the seat. if its comming and going and you felt it in the seat i would take a look at the carrier bearing.

if you are 4wd the front bearings are not servicable. they must be replaced as a unit. and they are anywhere from $300 to $150 for a assy. obvious that the 300 one is a factory. i would put it up on jackstands and run it in 4wd. set the cruise around your speed that you are hearing the noise and use a mechanic's stethascope and pinpoint the noise. no need to replace what's not broken. also offset wheels and big offroad tires are hard on these bearing sets. there are conversion kits to make them like the old spindle and needle bearing. i would reccomend that if you have aftermarket wheels and tires.

I was going to pull it apart and basically follow this write up:

http://www.guzzle7pt3.com/nblube.php

I just did my f250 for the same reason... It is an 05 250.....parts were outrageous. I beleive it was $1800 something and only like 300 labor, but it drives and turns much better. They redid my whole front end assembly at 138k

Sounds like wheel hub bearings to me. Mine acted similar on my Chevy 2500hd. You could feel the vibration more on smoother roads.

Just jack up the front end up and see if the wheel has any vertical movement. It almost feels like the entire wheel is loose.

BTW, mine were about $600 per side to fix at the dealer.