I just bought an 03 g35 coupe last week. It has 104,xxx on the clock, 6spd trans.

It seems to grind going into 3rd gear quickly, whether upshift or downshift. I have not experienced a problem like this before and is leading me to believe it may be the 3rd gear synchronizer.

From the research I've done this seems to be a notorious problem. Now what my question is that it seems as though when you double clutch into 3rd, or shift slowly, there's no grind....

Would it be worth it to flush the trans fluid to see if that does the job? I really don't have the time or money to tear the transmission apart.

 

replacing the fluid could help. idk bout the double clutching thing but shifting slower will help

 

I'm in the same boat bro. Seems like 3rd is on the VERY brink of starting to have a problem. I just did a fluid swap and that seemed to help a bit, but unfortunately, our cars don't really mend themselves and I fear we both will be looking for a CD009 here shortly.

 

Try flushing the oil, put some Redline shockproof in there and see if it helps. I doubt it though, usually Redline oils will only benefit the gearbox if it is not yet completely ****ed..

However, i too had the same issue as yours but mine was 5th gear synchro. I also had a huge amount of trouble changing into 3rd gear at high rpm. BUT, i have literally just got a brand new CD009 transmission installed yesterday and it is AMAZING paired with Amsoil gear oil. Very smooth shifts and no issues. $1695 brand new from Coz @ ConceptZperformance. Looks like your going to need a new box if the new oil doesn't fix it. Don't bother rebuilding either, will cost just as much as a new CD009 if not more and the synchro's will fail again in time.

Hope this helps!

 

Yeah I think I may be in the same boat, I bought my 03 coupe back in September and it had a heavy duty clutch installed. The idiot who installed it didn't upgrade the notoriously cheap pivot ball that comes in these cars so about a month after purchase it sheared off going down the road. I was told that when i get it fixed i might as well replace the clutch and flywheel. So I left it sitting in the garage for a couple months until I had the money for the repair and a couple weeks ago i had a mechanic friend of mine fix it for me with a new Southbend OEM clutch and lightweight flywheel and i went ahead and upgraded to a steel clutch line and beefier pivot ball and clutch fork. For some reason the guy couldn't get the clutch bled out right so i had to pump it to get into first gear. In addition it was now grinding going in to third gear. I took it to a local shop and they bled the clutch and so now it engages and everything just as it should, but still grinds going in to third gear if i dont shift slowly. Double clutching doesnt seem to really stop the grinding either. Im just ready for this saga to be over, any ideas/suggestions? If its the synchros going out i think i might just set this car on fire lol

 

it happened to me at 2nd and 3rd gear. so if i wanna go smoothly, from 1st to neutral and to 2nd gear, from 2nd to neutral to 3rd gear. but it wasn't happen for downshift.
any suggestion? i wanna try to change the transmission fluid first and feel the different.

 

Dude seriously? Did you even read this thread? If your synchros are going bad changing fluid won't fix the issue, get ready to buy a new tranny.

 

^relax old man before u get a heart attack. its doesn't hurt to try changing the fluid first before dishing out big bucks for tranny repairs

 

redline tranny flush helped my 6 gear grind. Took a thousand(two?) or so miles to fix it, and now you can't hear it.

 

is the Royal Purple good for G's ??