Stepper Motor Issues

Hey, everyone. My only problem I seem to be having with my printer now is that my Y-Axis motor grinds quite badly when printing. Here's a video. It should be quite clear when the grinding is happening. It is much louder in person.

[www.youtube.com]

I can't think of any reason why this is happening. It is the biggest stepper motor, if that has anything to do with it. It doesn't have any effect on the prints, it's just extremely loud. Any help would be amazing!

check to make sure the motor is getting enough power

I have similar noises during similar print moves, but not coming from the stepper motor.
Check your linear bearings.
If they are out of grease the balls inside start to rattle, indicating it is time for a good clean uout and re-grease.
The sound in the video does not sound like a stepper motor to me.