I just bought this manual 2004 350z with 29k miles on it just a month ago and I’m noticing that when I’m trying to shift out of first gear at about 3k rpm’s or more it feels like it’s slightly stuck in first and takes a little force to get it out and then when I try to shift into second there’s usually a grinding sound for a split second until it goes into gear that you can slightly hear and definitely feel in the shift ****. It’s not a high pitched grind and is more of a clunking feeling and sound. I’m noticing this type of grind with 2nd gear the most but it will sometimes occur in the other gears aswell and I believe this grind is more prone to happen in higher rpm’s though I haven’t tested it much as I don’t want to damage anything. I recently got the transmission fluid changed at a Nissan service center and changed the clutch fluid myself which I found didn’t make a huge difference. I then tried to adjust the clutch pedal to what some people said worked for them (3 threads showing out of the master clutch cylinder fork) and that seemed to only make it worse and extend my free play so I put it back to what it was before (about 2 threads).
I often find I need to hold in right above 2nd gear for a couple seconds before it likes to fully commit or else it will have the clunky grind and other times I find that doesn’t work and I just have to force it into gear after holding it just above the gear for a bit which does not make a grinding noise. I do feel like it tends to grind more with colder temperatures and is more smooth once the car is properly warmed up. Another thing I might add is when I push in the clutch sometimes it squeaks from under the car and I believe it only squeaks when the cars already warmed up though I don’t know for sure as it’s inconsistent. The squeak isn’t audible from inside the car besides this one time when I was at idle with the stereo off I could hear the squeak but usually you can’t hear it inside the car. From the outside the squeak is louder and definitely noticeable. If anybody could help identify what the problem is that would be great! In case this is helpful to you guys the current temperature around me is ~27 degrees lowest and ~42 degrees at the highest and I currently have about 1 inch of free play in my clutch

 

The transmission on the Z33 is a little "clunky" or "notchy" compared to other MT-equipped vehicles. But, there should not be an audible "grinding" noise.

Do you know what manual transmission fluid was used for the change? Last MT fluid change, I used Redline MT-85 GL-4 and my shifts are smoother. At cold temperatures, shifting is a little notchy, but it gets smoother as it warms up. This is normal. Physics.

The "squeak" noise that you hear when engaging the clutch could be a failing or "sticking" slave cylinder. It seems like that would make the most sense if the slave cylinder is not fully engaging which is causing hard shifts and grinding.

Another possibility could be the throw out bearing, but that doesn't seem terribly likely given the low miles unless the PO put a HARD 29K miles on it. Also, you don't describe any type of screeching which goes away once the clutch pedal is depressed.

 

It looks like they put in the usual oem fluid which is Nissan genuine MTF 75W-85.

I wouldn’t say that the grind is very audible, if you are listening closely with the stereo off you can hear it as a passenger. It’s more noticeable as the driver though as your able to feel the clunks through the shift **** and you can tie that feeling to the sound.

I was considering that it might just be how my transmission is but I have read a few threads of people with years close to 2004 that were able to make their make their car shift very smooth with minimal problems so it was just making me wonder if my transmission is slightly out of tune and could be improved. Another thing that makes me concerned that something is up with the transmission is that the shifting has been getting slightly worse over the course of owning it as when I first started driving it I don’t recall 2nd gear being as difficult as it is today.

 

Another possibility is it could maybe be the shifter alignment plate. Probably not unless someone has adjusted it recently (or dropped the trans), but it's another thing to rule out.

You previously mentioned that you changed the clutch fluid yourself. What fluid did you use? Are you absolutely sure that you got all the air out? The OEM hard line routing of the clutch line has many loops which like to trap air bubbles. Since air volume changes with temperature, that could be it. The clutch bleeding procedure in the FSM with OEM components is extremely finicky.

Years ago (maybe 10 at this point?), I had the infamous clutch pedal drop issue so I replaced literally everything when I did my clutch/FW - the master cylinder with a Wilwood, changed to a braided stainless clutch line, new slave, new pivot ball, throw out bearing, pilot needle, all fluids. I primarily did this so I wouldn't have to worry about air bubble issues when bleeding and I can now use a power bleeder with the right cap adapter for the master cylinder reservoir making it an easy one-person job.

But before you go down that route, I would do the easiest things first:

Check the MT fluid level. Even though it was done professionally, you never know.
Confirm the clutch fluid level is at the correct amount.
Verify no air in the clutch line.
Confirm the master cylinder and slave cylinder are fully engaging and disengaging properly. You'll need a second set of eyes to watch the slave underneath when the clutch pedal is operated.
Make sure the shifter alignment plate is in the proper position.

If none of that works, then it sounds like the trans may need to come out for further inspection.

OR, what you're experiencing could be the normal notchy shifting of our Z33s

 

Just my 2c on the topic.

The vehicle is low mileage but I assume also spent a lot of time if not most of it's life in the Seattle area? You have very cold winters there and it sounds like the car was probably stored during the winters. Although the mileage is low, the vehicle is now over 20 years old. The throwout bearing could be rusted/corroded, grease doesn't last forever on these since they are not sealed, but the symptoms you described doesn't match up with a bad bearing, maybe the squeaking noise, but not the grinding or heavy resistance when shifting.

This leads me to believe that you should have a 2nd look at bleeding the clutch hydraulics. Also, pull back the dust boot on the slave cylinder rod and check for fluid leaks there. There should be some silicone paste/grease, but nothing watery inside. If you see hydraulic fluid behind the boot, then you have a leaking slave cylinder and need to replace it, then of course thoroughly bleed the system again. To do this correctly (according to the FSM), you really need two people. It's a lengthy process. For good measure I usually will do one bleed session then let the car sit for a while (overnight) and then do a second bleed session. Alternatively, I might drive it for a few weeks, then come back and bleed it a second time. This is a bit extreme and I only go this far when I'm replacing entire components like the clutch master or slave cylinder.

Next, I would give the Redline MT-85 a try, even though you had it professional serviced by Nissan, they could have put in the wrong gear oil for the Z33 6MT.

Lastly, the transmission itself could be suffering from internal synchro wear, perhaps it had a very hard previous life. This is not uncommon on the earlier 03-04 350Z 6MTs. If this is the case, then we're talking replacing the transmission, and if you go that far, then you may as well replace the clutch and throwout bearing. I'm hoping it doesn't come to this. Note: The best 6MT for the VQ35DE equipped 350Zs is the CD009 which can still be purchase new from Nissan.

Good Luck!
-Icer

 

I used DOT 3 brake fluid and I was already planning on redoing my clutch fluid change as I wasn’t too confident that I got all of the bad fluid out. I’m also unsure if I did get all of the air out, it was difficult to efficiently bleed the clutch as the tube I was using to fit over the bleeding nipple was just slightly too big so overtime it would fall off. I should probably add that the clutch pedal has squeaked even in neutral at a stop so I don’t immediately believe it has something to do with the throw out bearing or the clutch although maybe it could be the slave cylinder.

From what I know though the PO has stored in a garage for most of its life and she didn’t seem like the type of lady to drive it very hard. I also believe she took it to a Nissan dealer every time it needed some kind of maintenance so it’s fair to assume she wasn’t touching it too much.

if I could avoid replacing the transmission fluid again I would prefer that as it already took a chunk of money to take it to the Nissan service center, but if that’s what I gotta do then that’s what I gotta do.

 

DOT 3 is fine. If you're doing it all over again, you could even use DOT 5.1 (not to be confused with DOT 5) since it is also glycol-based.

If it were me, I would go ahead and change out the OEM hard line for a stainless clutch line. It's a relatively inexpensive swap for both the upper and lower lines and it eliminates bends where air can get trapped. The slave cylinder is fairly cheap as well.

If you do try rebleeding the system, check inside the master cylinder reservoir to see if there's any gunk or build-up in there. With the low miles, it was probably still original fluid when you got it.

 

Yeah the it was the original fluid and it was very dirty and dark. There wasn’t much gunk in the reservoir but if I wanted to look in the master cylinder for something how should I go about that?

also i found this video online that shows a squeaky clutch which has a very simular sound to the squeak my clutch pedal was making although it does seem to have stopped since i changed the clutch fluid so im not sure whats up with it. Although it does seem to have stopped since i changed the clutch fluid so im not sure whats up with it.

 

That noise could just be the pedal clevis pin/fork assembly. Basically the hinge pin that connects the pedal to the master cylinder rod. It probably needs to be re-greased. I would also add some silicone paste to the rod assembly. Nothing to seriously worry about, unless you find that your clevis pin plastic bushings have broken and fallen out.

I stand by my recommendation of re-bleeding the clutch hydraulics. DOT3 fluid is just fine, but if you're not following the FSM procedure, then you won't get a good bleed on it.

1) Rapidly pump clutch pedal 5 times and hold down on fifth (requires helper #1)
2) Open bleeder at slave cylinder to release pressure built during step 1 (requires helper #2)
3) Immediately after fluid & air squirt out, close the bleeder. Note: Helper #1 needs to hold pedal down until bleeder has been closed.
4) Repeat steps 1-3 until no more air bubbles are present. Make sure to periodically check the clutch master reservoir and top off.

Tips: It helps to have a bleeder bottle with a clear hose so you can see if you're getting bubbles, foamy fluid, or old dark fluid out (watch it transition from old to new). This process can take a while when you're working with freshly installed components, meaning you disconnected the hydraulic system and allowed air to be introduced. If you're simply flushing out old fluid, it shouldn't take very long, 1/2qt of fluid should be more than enough to flush out the old.

Good Luck!
-Icer

 

thank you guys so much! i will rebleed it and see how it goes