Then see if you can get the starter drive. My bet is the grinding you keep hearing is the drive slipping inside. They make a heck of a noise when they wear.
The drive should turn one way, but not the other if you try to turn it by hand. If it turns both ways by hand then it is toast. From the way you describe the sound, my bet the drive is bad.
But make sure you get the right length. May have to drive to a rebuilders to get the right one. Find a starter and alternator rebuild shop and go see them. They can tell you quick if the drive is bad.
