Ford F-150 (2004-2008) :: FX4 - Hum And Whine At Speed Above 20 Mph Or So

I have a 2004 F-150 FX4 4x4 with 80k with a 9.75 LS, recently I've had the truck start making a humming sound/vibration (similar to the sound/feel you get when crossing onto rumble strips, only not as intense) when at speed anywhere above 20 mph or so, its doing this all of the time. The strange thing about the sound is that is only occurs when I am driving completely straight or to the left, if have the steering wheel just slightly turned to the right of center, the sound and vibration completely goes always until the wheel returns back to center. also I've started to notice that sometimes (not all the time) at lower speeds when let off of the gas and decelerate. I'm getting a very high pitch whine that sounds like a metal-metal sound but only lasts for a few seconds then goes away.

I cant tell where if the sounds are coming from the front or back and i cant decipher which side it is coming from. Also, I don't know if it is related but over the summer, probably june or so, i had to drain the fluid from the rear end and replace and add an extra bottle of friction modifier to get rid of the shuddering problem alot of people with 04's have run into.