Hi all, long time listener, first time caller. I have a 2006 Civic with about 70,000 miles and and manual transmission. Today, while in neutral and traveling at about 10 mph I revved the engine a little bit to engage 2nd gear. When I gave it gas I heard a slight "grinding" sound that sounded like about 5 gear teeth clacking. I drove around a little more to investigate and I found that when in neutral and traveling between 5 and 10 mph I get this grinding noise intermittently and it varies between 1 and 5 gear teeth clacking. I get the clacking very occasionally when I'm stopped and rev the engine, and never get it above 12 mph or so or when the car is in gear. The transmission still shifts very smoothly and does not grind into gear like transmissions usually do when the synchros are going. Any ideas?