Does anyone else's Z do this...?

Steps to reproduce...

-Get up to speed in either 3rd or 4th gear.
-Bring RPM's above 4000.
-Remain in gear and slowly let off gas letting the car naturaly decelerate.
- Keep you hand on the shifter.
-As the engine slows and drops beneath 4000-3500rpm you should feel a rumble in the stick and may even be able to hear it if you pay attention.

It's hard to describe, it's like the engine changes tone... from normal to a droney rumble.

Is this due to back pressure in the exhaust? Is it normal? Or is something wrong with my Z.

Any ideas? to me it sounds like the engine might be starved for air when not under throttle or something.

I believe my Z has always done this.

Any ideas?

 

I posted a simular issue a few months ago and recieved no replyies of value.

I have the same issue with my Z. It started at aproximately 6K and has gradually worsened (now at 27K).

Two dealers have yet to find a reason or a cure.

What is your millage?

 

I'm at 13500.

As far as I know, this has always happened and does not seem to be getting worse.

I have two thoughs on the matter, either it's normal exhaust backpressure.
Or, it's due to the design of our plenum; I've read that our plenum's design has a hard time providing sufficient airfolw to the two front cylinders. During accel air really gets sucked in but during decel, the air flow through the plenum may not be sufficient to keep the engine turning smoothly.
I'm no mechanic so this is just a guess and my gut tells me it's no big deal but I'd like to find out for sure.

 

I have the same problem also, dunno what is making the noise but I suspect it's transmission related.

 

Have the same. I think it's the tranny/flywheel harmonics.

 

I have it. 18K miles, and I also think it comes from mthe tranny/clutch/flywheel... I took my car to be checked for the synchros and Nissan decided they were ok, so I am just waiting for thetranny to blow up or something and then they can fix it anyway... idiots!

 

I really don't think it's the tranny although I could be wrong.
To me it seems like it's the tone of the engine that changes.

I really wish someone with mechanical skills would check out this post and gives us feedback.

Have any of you who think it's your tranny had a tranny upgrade yet or are you still on the original?
I'm on the original tranny (wish it would break so I could get new one while under warranty) and my car is an 03. How about you guys?

 

One of my fellow club members mentioned that one day at the track can take the tranny "over the edge" while daily driving might not. I don't trakc, but he does, so I was considering attending the next track event and let him take it out.

Slowly but surely it is harder and harder (instead of easier) to get into gear. It even makes a noise (like a deceleration) when I try to push it in. But Nissan still claims this is "normal". I have driven the car since new, and I know it is getting worse.

It is not about abusing the car. It is about somehow convincing the dealer that something IS wrong, which seems hard to do.

The rumble, I am going to try to reproduce it regularly in the next few days and then see what the dealer says. Until now it only happens now and then (or at least I only notice it now and then), so I haven't been that concerned about it.

 

The reason we think it is harmonics on the flywheel is several :

- It happens on deceleration
- It happens about the same range RPMs, as you come down
- It happens with the clutch out (engaged) (if you push the clutch in it goes away)

So somehow, as the car decelerates in gear, it reaches a point where these rumble/vibration comes on, and then as you slow more it goes away... at least that is what mine does.

 

Yeah, Slaponte that is the way my car does also.

It seems to me to be almost like something gets in a bind on deceleration. Not really sure, but I know the car didn't do it at first. I noticed it on my car around 15K. I now have 20K on it and it seems to do it more often.(might be that I am more conscience of it now) but the vibration/rumble hasn't gotten any worse or changed in the rpm range it occurs.

I really don't think it's anything to worry about, but I am glad I am not the only one to notice it. Maybe someone will figure it out soon. I know my dealership doesn't hardly have the competence to do an alignment, much less have to think or deduce what could be making an intermittent vibration/rumble. So I guess I will live with it for now.

 

it HAS to be sometype of Harmonic thing. I have had it since Day 1, I had a new tranny put in based on another problem, still does it (has nothing to do with the tranny as a fuction, but might have something to do with backpressure and the harmonics cooresponding to the tranny or RPMs). Also had with with the stock Plenum, seemed to decrease a bit with the crawford, but I am not 100% sure there is a relation???

in other words

1. It isn't caused by a failed Tranny
2. It probably isn't the stock plenum, but might have a relation?

 

Well, it does seem to be related to the load it's bearing, so I suspect something out of line or binding.

Maybe bad universal joints or something just a little loose that it binds up and gets out of line on deceleration? Driveshaft could be slightly out of line or balance, but I would think if it were a balance problem it would happen both accelerating and decelerating. But if you are accelerating quickly it may not have time to vibrate on the way up the rpm range, and have too much torque on the drivetrain to vibrate. Just thinking aloud and hoping something will show itself soon, or maybe jog something in someone's memory of a similiar problem.

 

I haven't done any research to support this but I think that the problem may be coming from the dual mass flywheel that is used in the Z. From Sport Compact Car's website:

Big, strong gearboxes like the one in the 350Z tend to rattle and groan like a UPS truck at low rpm. The noise comes from torsional vibrations originating from the surge of individual power strokes. A dual-mass flywheel separates the crankshaft and clutch sides of the flywheel by a set of springs. Using the power of math, Nissan engineers chose appropriate spring rates and flywheel mass to damp out these vibrations, making the gearbox smooth and quiet and eliminating complaints from those who would whine about funny noises.

I'm guessing that the vibrations you are feeling on deceleration with the clutch engaged are the springs between the two flywheel plates compressing and releasing as the tires are trying to keep the transmission spinning at the current speed (via the rear end), while the engine braking is trying to slow it down.

Just a thought....

 

Could it be b pipe in muffler rubbing on rear cross brace? Mine just started to do that recently. You can hear it and feel it. It is a rumble type of thing. I think the rubber exhaust hanger is getting warm and causing it to stretch more. I have plenty of clearance and it is hard to believe that it is moving that much. You can move it by hand that much and see exactly where it is rubbing. I have never heard it happen on a stock exhaust, but I have experienced it on several aftermarket exhausts on several cars. Worth checking. I would have never thought it was the exhaust making the noise, I had just thought it was my JWT flywheel.

 

Referencing my experiences witht this, I find the harder I accelerate (worst case, in 3rd gear, decelerating to aproximately 3000 RPM and floor the the gas pedal fast. I mean snap that pedal down.) the more prononced the rumble-vibration.

I have noticed the vibration in all gears except 6th under varying conditions and to varying amplitides but almost always between 4500 and 3500 RPM. The above 'worst case' resultes in the vibration almost every time with my Z.

I finally have found a dealer that believes this is not normal........

The Z is with him for an attempt to cure. I will post whatever comes of it.

 

Omited small detail in above 'worst case', accelerate to 4500 RPM or better, gently remove foot form gas and allow to decelerate in gear.

 

hatebobbarker's Z has a weird resonance with test pipes in the RPM range that you describe, when you decelerate. Maybe it's the cats being broken in?

 

29,000 miles and the 'rumble' has become more noticable as the miles accumulate.

 

Bump to the top. Found this thread by searching and even pm'd the original participants but haven't gotten any answers that could resolve this problem. My car has begun to exhibit this exact behavior. I can get the transmission to rumble repeatedly by doing a rapid (foot to floor fast) acceleration from aprox 4K rpm while in gear and then allowing the rpm to decend in gear to below 3K rpm. At aproximately 3500 rpm the rumble/vibration starts. Disengage the clutch, let the rpm fall to idle and the issue is gone. If I accelerate to a higher rpm, aprox 5.5k the rumble will begin around 4k rpm and be more harsh. This began around 74k miles and before I installed a MD 5/16 basic spacer. Only other mods is a drop-in filter and nismo exhaust. Anyone have this similar problem?

 

Wow. that was a long time ago. Yet, today, my cart still does this but at 64K miles it hasn't had any ill effect. It just does it and I ignore it. I have never had the traqnny out for any reason and I am almost positive is in there somewhere, in the clutch rotating mass area.