grinding at 35mph /oil leak

[koen]

06 ford explorer grind a 35 mph but not while turning
any body know why thanks

 

[Rcflyer330]

Well does it get louder with speed? Does it happen when you apply the brakes? If you turn the steering wheel a little bit does it get louder? Could you explain the grinding noise does it sound metal on metal or something else?
Sorry for all the questions but more info will help narrow down possible areas that could cause the noise.