Big sound when changing gear

Okay, please bear with me because I never heard the sound. If it is a banging when you shift between gears, I would start by checking motor mounts to see if one has broken. The engine can move around when shifting and bump things causing a noise. If you hear a grinding noise when starting it, it could be a problem with the flywheel. They can crack and make noise or you could have some broken teeth on it. If you can upload a video so I can hear it, I might be able to better diagnose the problem. Most people place them on u-tube and the I can go there to hear it.