Hi there Behnam_1,
Sorry that you are facing some issues with your WD drive.
It may be a good idea to start with just backing up the data stored on the drive. Grinding noises are not really a good sing when it comes to external drives.
After that, you can re-seat the drive. Use different cables(SATA+power) ones. You can even attach it to a different port.
What testing tool have you used. Even though you've already tested it, it will not hurt to run both short and extended DLG tests:
http://products.wdc.com/support/kb.ashx?id=WwBPF9
Is the drive under warranty?
Let me know how this goes,
D_Know_WD