Hello! I'm not sure if whether or not this is the correct spot to post this type of question but if I'm wrong, I'm sorry! I hope I can provide enough details without needing a video but if clarification is needed, I will provide.

I am the third owner of a 07 G35 coupe with a 6 speed manual transmission with 107xxx miles and it has recently started to get some problems. The shift from 1st to 2nd gear has now started to making a clunking/grinding noise. If it doesn't clunk, it grinds. If it doesn't grind, it clunks. In order to avoid this problem, I would always have to sit on the clutch a little while longer for it to be able to shift smoothly into 2nd gear. I have flushed out the transmission fluid and replaced it with Redline MT and the problem still seems to be there. At times the gear would go in smoothly, but most of the time it's always making noise. To add to this, 2nd to 3rd gear has started to make that clunky/notchy sound and downshifting from 6th to 5th (with rev-match) sometimes starts to grind. I know these CD009 transmissions are built much better than the previous transmissions the G's used to use but I hate to think that it's the synchros that's going out. I've read around several forums and gotten several different answers which doesn't really seem to help on my end. Can someone help?

 

There's also a chance the clutch master and slave cylinders are getting a tad worn or the.fluid needs bled. You might be just barely disengaging the clutch.

Probably synchros though. At least the 6MT is easy to rebuild

 

Idk if you still fixed it I’m in the same boat as well from first to second grinds if I don’t hold the clutch for more than a second. Also if I down shift without rev match it’s okay no grinds but if I try to rev match on any gear it grinds

 

First thing I would do is bleed the clutch to make sure you're getting full disengagement.

However you have an earlier CD00# tranny and they're notorious for wear due to fewer synchros on those early gears.

 

Ima try to bleed out the clutch this week, but when I did the engine swap when my second gear started to grind before engine swap would never grind also when rev matching wouldn’t grind with the original engine now with the new engine even if I try rev matching it would grind bad and wouldn’t catch it in gear only when I down shift regular it’s okay so idk really confused

 

An easy way to test if you're getting full disengagement on the clutch is shifting through all the gears while the car isn't moving. Engine running, use one finger on the top of the shifter and push through each gear, does it smoothly go into gear or do you feel it binding up. If it binds up or grinds while the vehicle isn't moving then you are not releasing the clutch fully.

 

so before the engine swap the transmission never grinded, but when I swap new engine problems came where I would go first to second quick and gear would grind and same thing for other gears if I changed quick, but if I granny shift gears don’t grind if I hold the clutch down for a few seconds, you think my clutch could be the culprit or that I need to bleed my clutch out ?

 

It's hard to say, some possible reasons for the clutch not disengaging after an engine swap would be:

-Clutch friction disc installed backwards.

-Throwout bearing carrier-to-clutch fork spring installed backwards (you can see this one by taking off the rubber boot for the clutch fork).

-Slave cylinder failing

-Master cylinder failing

-Air in the lines.

If you didn't touch the slave cylinder except to unbolt it during the swap I'd be leaning towards a clutch being backwards but you usually know something is wrong because the clutch is REALLY not disengaging, like if you take your foot off the brakes while in gear it will start pulling the car forward.

The throwout bearing spring being backwards will typically cause the clutch pedal to not return to the top position, instead the clutch pedal will be sunken about halfway.

 

It’s weird the car drives perfect only grinds from first to second if change gears quick I’ve seen that my clutch fluid is black so ima change it tomorrow and hope for the best also you think clutch placed wrong if so wouldn’t I have clunky gears on all gears ? Also when I down shift normally no grinds if I try rev match while holding clutch down heat gear grinding like doesn’t want to catch itself and grinds when trying to be put in gear. All gears feel good to be placed in so I’m confused if my transmission is bad or something else

 

Yeah if it's just the 1-2 shift it's likely worn synchros, you can try changing the fluid out to Redline MT-85 which helped my old tranny out significantly.

 

it’s every gear if I try to change gears quick has a quick grind from the clutch ima swap it this weekend also the flywheel hopefully it fixes it