Starter is making loud grinding noise, how do I make it stop with the shims?

After about 1 1/2 months of driving with the new starter in, it started making that noise everyone was telling me about. So I put 3 shims in that were provided with the starter, 1 by 1, checking every time I put another one in to see if it made a difference when I started the vehicle. There is 3 shims in now, thats all they provided and it still makes the noise. There was also a metal pin about taped to the shims, what would I use that for? Any suggestions on what might be going on and how I can fix it? Or did I maybe get a bad starter?