I've had the noise since I got the car and I brought it in to the dealership and they said it was the transmission. They swapped out my entire transmission and the noise is still there. I left it for the dealer to look at again and went out of town. He called me while I was away and said that he drove another 6sp and heard the same noise but the noise on my Z was quieter.

It's not very apparent when the engine and transmission are cold except if your going up a hill. When things get warmed up it happens under any sort of load. I wish I could describe the noise through words, but I can't. I know it is coming from the rear though. Is this something common with the differential in the Z car? You can only hear it for the first 2-3k of the tacometer before its drowned out by exhaust/engine. Like I said before it happens even if you gently go from a stop, or if you do an aggresive launch.

I just got into town and will be going to test drive a couple other cars to see if it is apparent in those as well, because at this time they are not going to fix anything because they say nothing is wrong.

Any thoughts?

 

Ok, I went to the dealership today and test drove another 2005 350Z 6sp with a diff. The car made the exact same noise mine does when you accelerate from a stop under any type of load.

If you gently accelerate you can hear it but it isn't as rough sounding as it is when you accelerate hard. Additionally, going up a hill from a stop really makes it happen.

My question now is this. What kind of material are the axles made of in the rear of the Z. If they are some type of composite metal then maybe the sound I'm hearing is the axles flexing under the amount of torque the car puts out from a dig.

Any thoughts?

 

What you're hearing is probably the clutch/throwout bearing chattering. This is very normal for our cars. You should be able to hear that noise with the car idling in neutral and the clutch disengaged (you not pressing down on the pedal). Even though the chattering does not happen 100% of the time and it can differ in loudness/pitch, this noise is more noticeable if you do this inside a garage or next to a wall; the noise goes away if you depress the clutch pedal all the way. Regarding axle noises, our cars also have a TSB dealing with axles "clicking" when coming to a stop, but I don't think that's what you're hearing.

 

Thanks for the reply. Chattering is a perfect word to desribe the noise I hear. It goes away (or is drowned out by the exhaust/engine) at around 2.5-3k RPM.

When I first crank the car up in the morning and drive it out after the temp gauge starts rising I can barely hear the chattering. Once the car is warmed up pretty good is when the chattering becomes louder and more apparent.

As long as its normal and nothing is going to break then I'm fine with it. Its barely audible with the windows up and the music turned off, but who the hell drives around with no music on and their windows up? lol

Anyways, if anybody else knows what I'm talking about let me know so I can feel even more at ease

 

My thoughts are don't worry about it. Drivetrains make noise. You know nothing is wrong, so you gotta live with the noise.

 

is it that mechanical whirling sound?

 

I dont know, but chattering was the first thing that sounded close to it. Once you start rolling and accelerating it goes from a slow chatter to a fast chatter then disappears.

The funny thing is, it doesn't make the sound on the automatic that I test drove. Maybe it has something to do with the gear box like milanista suggested.