Grinding in startup?

My chevy silverado grinds on start up very bad, on quiet mornings you can hear it a block away when I start it to leave for work. A neighbor heard it and said he thought it was the starter and fly wheel grinding together because of wear, after a few weeks it finally went completely out and once again I was advised while broke down on the road that it was believed to be this problem, after getting the vehicle home my mechanic looked it over and concured he then proceeded to repair the problem two weeks later I have the same problem I returned it to him and he recommened shimming the starter this has not worked I personnally do not believe that he replaced the fly wheel the starter of course is a remanufacture and now he's telling me that maybe i should go to the dealer and by a dealer starter that this will hopefully solve my problem. What do you guys think should I follow his advice or look for someone else to do the job correctly I starting to have suspicions of this mechanic