My 97 f150 4x4 xcab has developed a low pitch squeal(interior) at about 55 mph .The truck is a standard and it makes no difference if you take it out of gear or shove the clutch the noise remains until it goes down below 45-50.It doesn't sound like it's coming from the outside,it almost sounds like a noise through the speakers.I've turned the radio completely off as well as the heater and the ear popping noise is still there and with the radio on you can still pick it out.SOMEONE PLEASE HELP ME AS THIS IS ANNOYING AS HELL!!!!!

 

Nobody has any ideas??????????

 

I had a similar such noise that at first I thought was a tire. It turned into a lower pitch, then into a bad pionon bearing.

 

Something speed related like that even though outside, can still sound like it is internal. Sound travels. Have you checked all door and window seals to make sure it isn't something like wind noise at that speed? Or maybe a drain plug causing that? Otherwise, I would start where Joe Gaddy mentioned. The pinion bearing. Best to catch it now before it becomes a problem that leaves you stranded or damaging other parts.

 

All my searchs are ending up with the same info so I guess I'll start there---Rearend ring and pinion.Thanks for your input,much appreciated!