Thought I'd post this just to show that it's not only RX-8s that can have little problems (actually I never had any problems with my RX-8 except weak AC)...


I got a G35 Sedan with 6MT last October. My tranny was slightly notchy in all gears until about 2500 miles (I assume because it was new and tight). From 2500-6000 miles it was superb in every gear under all conditions - a truly wonderful gearbox IMO, although the RX-8/Miata/S2000 ones are better.

Since 6000 miles I sometimes had trouble getting into 6th whilst accelerating quickly (e.g. when I went through 1st-3rd or 4th and then skipped to 6th at 80mph or so). It felt like I was locked out of 6th (like the lockout for reverse), but hitting the clutch a 2nd time always made it work. Dealership could not reproduce problem.

Since 6500 miles to present (7500 miles) I get a grind when moving into 6th gear (crunching sound as if the synchro-mesh is not working properly). It happens every single time under every condition. It is so consistent I can do tests around it: clutch fully down as far as it can go right to the floor (grind), high speed move from 4th to 6th or 5th to 6th (grind), low speed gentle move to 6th at 2500rpm from 5th (grind), count 2 secs before moving stick out of neutral to 6th (grind) etc.

The only way to avoid the grind is to double clutch (clutch pedal in, move to neutral from lower gear, clutch out, clutch in move to 6th, clutch out). Every other gear is fine under all conditions and driving behaviour, so now I am mostly avoiding 6th altogether.


I did a search on various G35 forums and it seems some people with grinding in certain gears need a new gearbox. Am I one of those people? Stay tuned to find out (I already have the answer but a little anticipation never hurt)...

 

That’s what warrantees are for.

Good luck getting the problem sorted out.

 

UPDATE TODAY

Took my car in to SouthWest Infiniti to see about the problem this morning. The service rep was smart enough to ask a service guy to drive the car with me in it to see if he could reproduce the problem. He takes off and runs through the gears stopping at 5th and says he doesn't see the problem with 6th gear. I say "Dude - you're only in 5th!". Actaully I never use the 'D' word. He puts it into 6th and there is the usual crunching sound. Lucky I was with him

I tell him the various things I've heard on the forums about what might be the problem:
1. might need adjustment of gate
2. might need new synchro for 6th
3. might need complete new transmission

He tells me that Infiniti won't let the dealerships take apart the gearbox to try to fix it - they can only replace the whole thing (and apparently Infiniti have released a new transmission since the early 2004 6MTs came out to fix issues so I would be getting that one). Infiniti also wants the transmission sent back to them for analysis to figure out why the problems are occurring (possible future recall?).

So I kept my car until the parts come in. Just heard from Infiniti that I need to bring the car in on Monday morning for a new transmission and clutch to be installed, and I can have the car back on Tuesday (will get a G35 loaner of course).

Aside from the annoyance of my tranny going bad (and I never did any high rpm clutch dumps, or racing/auto-crossing etc), I have been very impressed with the Infiniti service and immediate response. I suppose the transmission issue could befall any car (except Lexus of course ) - which reminds me my '02 Acura MDX has just been recalled today for transmission issues...

 

Have you been getting tire feathering on the front tires?

 

I asked my dealership service department about the issue as well. They told me so far they havn't heard any complaints in their dealership. The service manager also told me Infiniti will not allow dealerships to rip apart the tranny and try to fix parts of it, they'll just replace the whole thing. I don't have a problem with gear grinding though, except a couple times when I was shifting and the car hit some serious pothole.

 

I had the 6 speed in my old SpecV replaced twice. (its the same tranny the maxima uses but different bell housing)

I had the same problem as you except it was third gear.
Nissan (infiniti) was not allowed to take the tranny apart either. But it was replaced no questions asked.

And I did drag race and autocross my car .

 

Phineas - no feathering (I had to look up this term).

Skyline Maniac - Yes, the G35 gearbox problem might be rarer than I thought. My dealership tells me I am the first with this problem they have experienced (but then again I am the first 6MT sedan they have seen, although half their coupes are manual). And I have to say my dealership have been very good about things - I can imagine some manufacturers or dealers would deny the problem or defend it ('they all do that') or accuse the owner of causing the issue.

 

Tire feathering is a problem with the Z...not the G.