i have a 2005 gto with the ls2 and t56 transmission. it has 40k miles on it. all i have changed in it is a borla catback, mishimoto radiator and and billet jhp short throw shifter.. which were installed months ago. the past three days i noticed a sound coming from either the transmission, shifter or the clutch. its a slight grinding noise almost sounds like its whirling. im trying to pick point what it could be or where its coming from. it mostly happens when im going into third gear.. if i release the clutch it goes away.... please help

 

If it doesn't make the noise in neutral with the clutch in but you hear on upshift/downshift it could be the Synchronizers. I have limited knowledge of manual transmissions so maybe someone who works on them regularly will be able to you one way or the other.

 

Park car, run engine, foot on clutch and place it in any gear.

Is there a noise ?

If so, it cannot be in the gearbox as nothing is turning.

Also, as you say GTO...ie Monaro, spigot bearings seem to be an issue on a lot of those which can cause noises/issues....if that is indeed the problem it needs sorted asap or it can do a lot of damage.

 

I can shift into any gear while standing still no problem or grinding. I checked the clutch fluid it was black and goopey. I flushed it all out and bled the system. And topped it off to normal. And the dang thing is still grinding. It doesnt do it everytime. Maybe like once every 4 shifts.