2007 Mazda 3 Trany grind
 

Hey everyone. I have a 2007 Mazda 3, 70K miles. The trany grinds upshifting from 1st to 2nd sometimes but only when im accelarating hard and shift above 3500 RPMs. When i drive the car normally it virtually never grinds. I imagine the synchro is starting to go bad. What I'm wondering is if I will be doing any harm to the rest of the transmission by letting the synchro slowly go bad. Right now its not grinding under normal conditions and the rest of the transmisson/clutch is fine.

I figure I might as well replace the clutch when I eventually have to service the transmission, but I'd like to get some more life out of it. Any thoughts? Thanks.

Definitely sounds like a bad synchro to me - you can try double clutching, just shifting a bit slower (allowing the engine to slow down more and sync up the gear speeds without the synchro being used), and make sure your clutch is all the way down when shifting.
If you are going to do the clutch / trans at some point and keep the car - just plan for a new transmission all together. It is probably easier to just swap in a rebuilt unit rather than disassemble one to get the synchro replaced (I don't know the actual complexity, so ask a shop).
As for the damaging other parts question... the little bit of metal that is grinding away shouldn't cause any issues - that is unless a whole tooth or chunk starts flying around.

Good luck, and let us know how long it lasts from when the grinding started :)