It could be the disc brake covers on the inside of the rotor. One of mine was knocked up against the rotor and made a grindingand rattling sound that got better as I went faster. Worth a look because it's an easy fix if that is the problem! It could also be bad wheel bearings. Does it stop or change when turning? if it does, that would be another vote for bad wheel bearings.
Get your car to a garage immediately! No car should be making any grinding noises while driving. this may suggest a slipping clutch, faulty brakes or maybe even damage to the piston and combustion chambers. it could be either of them which is why this needs to be fixed as soon as possible.
my guess would be to have your brakes checked... or maybe you are dragging something...
Wheel bearing
No
if its while your driving it could be wheel bearings
Throw-out bearing................
countershaft bearing could be problem
Your brakes are dragging, likely the pads are worn down to the steel. Hope this is helpful, www.TunerTools.com
check CV joints, if bad replace shafts and joints assembly
The grinding noise you hear are your shocks and struts. If you experience bouncy while you are driving, as well, you should have them changed.
it may be the drive shaft u-joints if its rear wheel drive
no tranmission fluid in it or it maybe your tranmission is bad because you keep grinding your gears up but for a automatic its your transmission fluid