Loud squealing sound!? Help please

[spidermn]

I just notices this sound about a month ago. It sounds like the breaks are squealing off and on. This happens at random times and I have checked both sides of the front breaks and they are fine. I have also checked the bearings and they are fine as well. I have checked everything I can think of and am coming up with a blank. Has this happened top anyone or does anyone have any suggestions or know what it could be. The sound is coming from the front of the truck only when driving it above 20MPH. It is a high pitched sound. Please help anyone. Thanks