I just picked up this 07 350Z 6MT, 58k miles. It looks and drives like new. When cold, it can be a little hard to downshift into first and sometimes even second gear. No problems when warm. This doesn't bother me as it seems to be a characteristic of this gear box. (My previous G35 coupe was similar).

However. When it is cold if I put the car in neutral and let the clutch out, there is a little forward surge. The car does not roll if the e-brake is on and it does not stall or drop idle. But it definitely gets a little surge forward when I let the clutch out. On level ground, with the e-brake off, it will roll a little forward.

Otherwise, car drives great. Taking it to the track week after next.

The main reason I'm concerned is that the warranty is about to expire. If this is a synchro issue I need to either get it to the dealership of get an extended warranty. I may get the extended warranty anyway since I don't know how this car was used before and I do know it will be at the track 4-5 times a year.

 

clutch pedal engagement point possibly set improperly? the bad reputation on our 07's clutch slave cylinder does not help either.

if your vin falls under:

JN1BZ34**7M500002 to 552786
JN1BZ36A*7M650021 TO 654836

you qualify.

 

Thanks, I'll look into it. But what I'm talking about is with the clutch engaged (foot off clutch pedal), gear box in neutral.

 

Do not expect a vehicle to operate properly until it has reach operating temperature. Thats just common sense.

 

Excellent advice. But let me make sure I understand what you are saying: If the car is in neutral and you let the clutch out it is normal for power to be transmitted to the rear wheels if the gear box is cold. Even when in neutral.

Cool. No worries then. Thanks.

 

lol I love when people are sarcastic back at davidv

 

^This. The fluids in the trans will act different before they're warmed up. Mine does this too when it's really cold.

 

I noticed this on my '04 when it was up on jackstands. But it wasn't enough to move the car on the the ground. The only 2 things I think could cause this is 1: A bearing going bad. 2: Toasted gear oil. I would start off with changing your tranny fluid and while you're changing that out you can take a sample and send it off to Blackstone and they can tell you if you have a bad bearing or not.

 

if adjusted improperly, the clutch pedal can be fully released while the clutch is still engaged whether fully or partially.

 

Since N80 and I have just finished wrangling on a thread in the 350Z General forum over shifting and how transmissions work etc. I kinda vowed not to enter the exclusive boy’s world of tech threads ever again. However, since my one look into a manual transmission seems to qualify me as an expert here, I will venture an opinion.

When in neutral (foot off clutch pedal) the engine turns the transmission input shaft, which in turn spins the lay shaft and its gears, one of which, is in constant mesh with first gear. First gear’s natural state in neutral is to spin freely on the main shaft. (When selecting first gear, a shift collar that is splined to the output shaft, slides toward first gear and through the dog teeth on its side, locks the first gear to the output shaft. The output shaft will now flow power to the drive shaft.)

If you are getting any power to the rear wheels when in neutral, it would seem that your first gear-wheel is seizing to the shaft instead of rotating freely on it. If so, you need to get a repair “tout de suite” as it seems your warranty is about to run out.

My one venture inside a transmission was with my old MGB. One day my dad spied it leaking a tiny bit of oil. My dad ran a small mechanical and machine shop. Where amongst other things he fabricated parts to repair obsolete antique car transmissions. The leak was a quick fix, but my dad, being my dad, also ripped every part out of the case and set about fussing over and improving them. I whined that I was losing the last sunny days of top down driving, but to no avail because he had an idea to add a fourth synchromesh unit. The early MGBs had a non-synchromesh first gear. After he had all the parts ready and everything antiseptically clean, he made me get my hands in there to help assemble it.

I must admit that having that extra synchro made downshifting into first 'on-the-fly' ever so much easer.

 

HI,

In transmissions that use the thick 90W gear oil, it is not uncommon for the oil to be so stiff when really cold to actually cause the car to want to move either forward or backward when you let the clutch out in neutral. I could go into a mega length post on how this thick cold oil is actually causing a sort of fluid coupling, but suffice it to say that this is normal. My 2004 Z does it and an old 60's Pontiac I had did it as well. Now, my 90 5.0L Mustang has no issues with this, but the Mustang actually uses type F automatic transmission fluid in it's manual transmission. So that thing shifts like velvet whether hot or cold. In fact it always shifts smoother then my Z, whether the Z is warmed up or not. With that manual in my Mustang, Ford did actually have a better idea. The Z has to have the most heroic shifting I have ever experienced with respect to physical effort. My Z, when cold, is a royal pain to shift out of first and into second. In the summer it is fine, but with the temps in the 30's, it takes act of God to shift the thing until it warms up. Then it is fine. I don't even attempt to down shift into second or first until a complete stop when it is cold. Take offs are generally slow and use a 1 - 3 upshift. Again, this is only when the thing is cold. It has been like that from day one and now has 64K on it.

 

archangele, I think you are correct that this is a fluid coupling issue. This goes away completely as the gear box fluid warms up. The behavior of my transmission is identical to yours and similar to my 06 G coupe. Jennifer, I suspect you are probably right as to the location that the fluid coupling is occurring.

I was planning on getting a Nissan extended warranty anyway so if this deteriorates I'll still be covered for this and anything else that comes up.

Since I live in the south and the temp this afternoon was 68 degrees, I think I would just put up with this rather than switch to thinner fluid.

Thanks for the brainstorming folks.