Pulled the TR3650 out of my '03 Mach 1, 3rd and 4th synchros shot, replaced it with a rebuilt TR3650. Starter is now grinding when you try to start it, it will start and grind for a few seconds and then stop. Had no issues before. Tried a brand new starter and same thing. Flywheel is fine, no missing/chipped teeth. Can't figure out why it is doing this when it was perfectly fine before. The block plate was missing when we tore it apart, it only had a small piece of it surrounding the starter, it now has a complete plate. This is the only difference. Flywheel was not removed. Stumped.