steering wheel vibration HELP

[deuchant]

hey, anyone know what would cause steering wheel vibration at highway speeds? 65+mph
if i turn in either direction on the highway i.e. a long sweeping turn left or right, the vibration goes away. it's only while going straight. braking nor excellerating affect it.
i pulled the front tires and had them balanced, this seems to have helped a little.
the wheel bearings seem good, as well as the tie rods and upper control arms.
the drive axles seem good, no play, no torn cv boots.
the only thing i can find wrong is a little play in the lower ball joints, which i plan to replace and a bad diff seal where the drivers side axle enters the diff.
are there any more specific tests i can do to check the wheel bearings and drive axles besides just jacking the wheel up and pushing and pulling on it?
is there a way to check the inner tie rods?
thanks

 

[bovine]

You may want to check on your brake calibers I was driving my 94 one day stop at a red light fine took off and at 45 I could not hold the steering wheel.I slowed down and started smelling like something was burning pulled over and found out by my dad that it was probably a stuck caliber. So we released the pressure and it was fine for a few weeks then it didn't vibrate but I started smelling something and when I pulled over there was smoke coming from my wheel it toasted my pads caliber and rotors and I had to bring it home on the e-brake.