Hope someone has an idea what this is - slightly concerned it could be serious...

You all know the noise you get from the transmission when your foot is off the clutch is normal, well i seem to be getting the same noise only somewhat louder in 2nd, 4th and 6th gears. Noise seems to be emanating from the air vents but it definitely isn't air related because the noise disappears in 1st, 3rd and 5th gear.

Anyone any ideas Just had a new engine fitted and thought maybe that could be something to do with it but i think i noticed the noise before - at least in 6th.

Reckon i might try transmission oil change i suppose. Do mazda reccomend this after a certain mileage or is it just general good practice to do it?

 

I guess I know what sound you are talking about.
(Step to the very end of your clutch and release it quickly then the noise comes out)
it happened to my 8 even I placed it in netural
I was told by my dealer, that my clutch is damaged if I really wanna get rid of the sound the only thing that could cease it is to replace it a new clutch.
and yes, after I get a new clutch I hear no sound out of my 8.

hope this could help you.
In my experience