Because either the brake pad is worn or the rotor is warped causing the pad to be heavily worn. Time for replacement front rotors and brakes. Check the wheel bearings ups front as well as the rear pads and rotors to ensure everything else is wearing OK.
Its hard to say... do u know where the noise is coming from?
depends on where the grinding id coming from
u joint on drive shafts
Does it only make noise when in 4x4 mode or all the time?
Brake pads are worn out=========Replace.
sounds like the brake pads in front or back are worn out, if so need to change them before driving.
It depends on where the grinding noise is coming from. Most of the time the grinding is coming from the brakes and the brake pads need to be replaced. If they've been grinding for a while, the rotors will need to be resurfaced or replaced. Other possibilities for grinding are worn axle bearings, or a problem with the clutch. If the clutch goes out, there will be a grinding noise when you try to shift gears.
Defective left front wheel bearing. Have this repaired ASAP, as it can cause an accident.
lower ball joints need lubed up or probably replaced.
The suspension is rubbing. There is a pad or bushing that has worn and is allowing metal to metal rub.
Jack up the car to suspend the suspected wheel in the air. Make sure to use jackstands so the car doesn't fall on you or any of your body parts. Spin the wheel. If you hear a grinding noise / vibration coming from the center you may have a bad wheelbearing.
If your vehicle has a mechanical speedometer it might be your cable rubbing against its casing