I've had a 3rd gear grind for a while now. I finally solved my problem by putting in my front motor (trans) mount insert. I've been using the side inserts for a couple of months and only now installed the front one. The mount was completely gone. Now there's no grinds even on hard shifts and i'm shifting hard with my new clutch. I still have to put in the rear insert as soon as I stop being lazy. Hope this helps somebody