So i've researched quite a bit into this and I'm looking for a recommendation on what to do. So I have an 03 350z 6mt. It's at around 96k miles now, bought used at 90k. After around 1k miles of driving the car, I noticed rare gear grinding going into 3rd gear, seeing as how I was a new owner I wasn't aware that it was a very common issue. (FYI, i've been driving stick for around 4 years now, never have had to replace a tranny or clutch or anything stick related, so I think of myself as a pretty good stick driver). Well a few months after the first gear grinds, it started doing it often. Then one morning it wouldn't shift into 3rd. It would just grind if I would try to and wouldn't allow me to. So for the past week i've just been skipping 3rd gear, going straight into 4th instead. Well, now my 4th grinds every time. There was no signs of it going bad, it just started today.
So, what should I do. I was thinking about replacing the whole transmission and hoping the one I get isn't having the same issue.
Would replacing the transmission fluid with the redline mt90 fix this?
Lastly, would it be cheaper to have the 2 gears rebuilt than buying a new transmission and having that installed?
By the way, I did the use the search button...google searches...youtube videos and I haven't seen anyone with the same issue as I'm having.
Thank you!

 

it might help for a bit, but it sounds like the synchros are going out.... prepare for new transmission cost. z1 has the cd009 for just under 1700 brand new

 

Mind as well buy a CD009, new or used it doesnt matter.

It sounds like the previous owner knew of the issue though.

 

I'm on tranny #5. It is a CD009.

The only good solution is to get a CD009.

Make sure you replace the pilot bearing, the throwout bearing, the clutch and pressure plate too. (My pilot bearing is shot, and my throwout bearing is noisy as hell . . . . )
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Yeah, it's your synchros. Happened to me last year, so I ended up buying a new CD009 from Z1.

 

Before you do anything, check for clutch drag. If your clutch is dragging, you will be killing your synchro's.

Jack the rear end up, put the car in 2nd and depress the clutch pedal. If the rear wheels spin even a little bit, you have found your issue.

Depress the clutch, put the car in 1st and rev up to 6000rpms. If the car pulls forward, you also have clutch drag.

If you have a SAC clutch, you most likely will have clutch drag and kill your synchros. A single hard launch will knock the adjustment loose and you will have notchy shifts. Pretty soon you will have gear lockout. Most 05+ have a SAC clutch.

IMO I think people are wasting money on transmissions. It could be as simple as pulling out the trans to free the input shaft from the pilot bearing to cure the bad synchro issue. Any clutch drag will give the same symptoms of bad synchros. Since Nissan used SAC clutches, I'm positive 2/3 replaced the transmission for nothing.

 

Can you rpm match into 3rd gear? If not replace tranny.

 

Are you referring to the change to a concentric slave cylinder design from an external slave design on the Z specifically? Or the SAC design that is incorporated into the pressure plate of clutches in general? If the latter please let us know where you learned about their change in design? Or did the 'change' to SAC design coincide with the Slave Cylinder redesign? Just trying to understand what you are talking about...

If what you say is true then why doesn't it grind in all gears?

Why was the problem primarily 03-04 cars until the CD009 revision came out in 05?

So the pilot bushing friction on the input shaft is causing shift synchronization issues as well?

Please, elaborate.

 

Were your other 4 trannys a CD008 or did you also have a CD009 go bad?

I've heard even those aren't bulletproof..

 

My other 4 trannys were NOT the CD009 model.

 

got a '04 with 80k miles and a '03 with 130k miles (both boosted) with no synco issues. I guess I'm fortunate...

Before you pull the trans make sure the clutch is adjusted and working right... I have seen similar shifting issues with master/slave, clutch adjustment, or bleeding issues

 

^Exactly a blown master or slave is a more likely cause of poor clutch disengagement

 

Generally 05+ will have a self adjusting pressure plate. Some older models may have had them installed. The change in design is the same typical LUK style SAC clutch, which is pure garbage. 16+ different failure points, all can kill a tranny.


I recently thought I lost my transmission. I could not shift into any gears while running. This was typical clutch drag, however once I got it "better", I was then just grinding severely in 1st, 2nd and 5th. 3rd, 4th and 6th went in like butter. It only got worse. A few days later I had total gear lockout.

I had a race weekend coming up, so I did about a week of sleepless research. The SAC clutch maintains pedal height as the clutch wears. The downside is a single clutch drop can knock it out of adjustment. The pressure plate is known to kill clutches and cause other problems.

To see if you have a SAC clutch, remove the slave, peel back the rubber clutch fork boot and peek inside. It will look like this;



If so, remove it immediately. You WILL kill your synchro's and clutch.

Cleaning the master is easy. If the clutch disengages near the top of the pedal, the issue is usually the pressure plate or input shaft binding on something. The input shaft must have little to no drag on it to provide complete disengagement. If the clutch disengagement is near the bottom of the pedal, generally you have air or a master/slave issue. Incomplete disengagement will eat a syncro.

 

I got all that...I asked WHERE you found this info...did you compare pre and post -05 clutch assemblies yourself?

While I am not disparaging your theory, you are being rather vague..

Thanks for the picture...and thanks for telling us to remove it...you still havent told us anything beyond "it fails because it goes out of alignment and causes clutch drag killing transmissions"

Thats like me saying...your tires are out of alignment which is why they are getting eaten up...instead of saying, you have too much front toe, resulting in uneven inner tread wear and increased road noise..one statement reveals the root cause...the other is what you tell the ladies at the counter of Tire Kingdom. We are not ladies in tire kingdom.

How did you get it "better"?? By removing the Self Adjusting Clutch assembly from your pressure plate?

Did you think that, maybe, your clutch drag was being caused by a failing master or slave cylinder? Ever wonder where that fluid goes as the level in your res drops...?? Just asking if you gave it consideration is all.

If the clutch disengages, using your words, there is no problem to begin with. No one contested that incomplete engagement kills transmissions, we are talking about why. Just trying to make sense of what youre trying to say...and you still havent said how or what in the SAC causes what youre saying. You obviously know the specifics right, so fill us in. Is there an inherent weak point? One hard clutch drop can messitall up...well then id be on transmission #17000 instead of #2.

So, you had complete gear lockout, got it better, then got terminal lockout again. Have you ever actually successfully remedied a failing transmission on the basis of your theory?

Is the SAC assembly the ...**lurking cause of the blight that has always plagued the new gen of Z transmission**mwaha ah ahhhhh

Again I reiterate, it seems based on what Ive read over the years that the issues with our transmissions have improved, which is contrary to your theory...clutch slave cylinder redesign aside which is debatable of course.

 

Here is a link with the concept that vibrations and a single launch can knock it out of adjustment

http://www.audiworld.com/tech/eng86.shtml

If you still have the OE 05+ clutch, is will have a Self Adjusting Pressure plate.




The adjustment can easily be knocked out of place as the clutch wears. You will either require more travel, or have too much travel.

This will cause the clutch disc to still lightly contact the flywheel, keeping the input shaft spinning. You can strip your synchro's without hearing any grinding. Any resistance means you are manually slowing down your synchros.

I got the pressure plate better by taking a screw driver with the pedal depressed and pounding the crap out of one of the ajustment-springs, counter clockwise. Although this didn't make too much difference, I could see the fully-relaxed position of the clutch fork had moved back by about 1/2". This meant the fingers of the pressure plate had pushed the slave push-rod back, but unfortunately it required even more travel to disengage the clutch disk.

The clutch drag was not caused by a master/slave cylinder. If the disengagement is near the top of the pedal, it's internal.

On a very slight hill, you can put the car in gear and check when it starts rolling back by slowly depressing the clutch pedal. The grab point was near the top.

Put it in gear with the clutch pedal depressed, turn on the engine and slowly release the pedal. The car starts creeping forward when the pedal is at the top.

On the highway, 60-75mph, depress the clutch pedal and see what your RPMs fall to. If they are at 1000-1500rpms, you are dragging your clutch/input shaft.

To check the master/slave. Pump the clutch pedal and see if fluid is moving inside the res with the cap off. Hold the pedal down with a block of wood and mark if the fluid has gone up or down after 1 minute. To check the slave, measure the push-rod travel distance from fully rested, to fully depressed. Place a block of wood between the pedal and seat, and leave the clutch pedal depressed for a few hours. If the fluid level and push-rod distance has remained the same, hydraulics are good, minus any air. IIRC the push-rod needs to move ~3/4" for it to disengage on a non-sac pressure plate.

Hypothetically, the transmission and synchro's should last the life of the vehicle IF the input shaft has absolutely no drag and the driver knows how to shift properly.

 

I appreciate the response. I understand what you are saying, personally I still think your theory is a bit hairbrained, but nonetheless could be a viable explanation for premature synchro wear. Prob going to need to be a bit more convincing to get people to pop their bell housing, re-install only to find that the trans wear is terminal anyway. Maybe like explain exactly how the assy becomes misaligned WHILE installed and operating.

The author of the tech article you posted is saying you need to RESET THE SAC ASSY in the pressure plate PRIOR TO RE-INSTALLING WITH A NEW CLUTCH DISC to prevent being installed in a worn position from the old clutch disc, which would mean the SAC assy would adjusted as if there is a worn clutch in place, rather than a new clutch disc causing the drag.

You're doing all this diagnosis and hunting, but the overarching problem might just be the inherent transmission design.

 

I was talking to BJ Zacharias and Brad Jaeger from the frontrunning Doran Racing CTSCC 370 team before their race at the 12hrs of Sebring (their race was immediately before the Tudor 12hrs) about their entry...I asked if they were running a stock trans and how it had been holding up. Funny they had to swap the trans between practice and qually...I had no idea but they were muted about the trans...

1min in is the trans swap...you will **** yourself at 1:33.

them boys fast...qually lap was a 2:16 race fast lap a 2:17