2000 Ford Expedition Vibration

OK guys... Here goes.  2000 A4WD Expedition Vibration... 210,000 Miles. Seems to
be in the front.  Details:

About 10,000 Miles ago, some grinding in the front, No vibration (not the brakes)..
Replace both front wheel bearing assemblies.  All Good.
About 5,000 miles ago, mild vibration begins and slowly gets worse.
About 3,000 miles ago, Brakes start to grind... Replace both Front Rotors and Pads,
no change in vibration.
Yesterday... Looking under car for possible sources.. I.E. suspension parts and
driveshaft... only thing that was definitely bad was the Idler Arm... replaced
immediately.  
As of now... vibration is still there.. details:  begins at about 25 MPH, gets worse until
45, then goes away... Comes back at 60 or so, gets worse till about 70, goes away
and runs smooth until as far as I pushed it (about 85).  NOW... this vibration is NOT
the engine.. I shut it off at high speed in neutral and NO change.  It COULD be
transmission, but severity of the vibration does not change at all based on delivery of
power, only speed.  The universals SEEM okay, but they've never been changed.  

SO... is it possible I got a defective wheel bearing? Or are the driveshafts still the
most likely culprit?  I doubt it's the tires/alignment, but if it is, that's the one job I can't
do myself.