Makita 13" 5103N 110V

We have two 5103N 's in our shop that we use. They cut well. Both have bearing type rattle noises as they slow down after use. I sent the motor and gear box out and had it checked by a Makita authorized repair shop and he sent it back saying that the " motor was fine " . Could the noise be coming from the gear box and he missed that ? Any help would be appreciated.