I've scoured the web seeking insight to this problem but every forum post i find seems to end unresolved about this issue with no definite solution so I turn here in hope. I have an 04 infiniti g35 coupe. I hear a rattle when i turn my car on and it's in neutral. if i press on the gas, rpms go up and the rattle seems to increase in speed. When i step on clutch in neutral the sound disappears. I just had the clutch and throwout bearing replaced and the sound is still present. I've listened to sound clips of bad input shaft bearings and that sounds more like a grind than a rattle. Can anyone here shed light on this issue?

 

i need to know the answer to this problem as well. except my rattling occurs between 1k and 2k rpm in gear of course. past that range the rattling stops.

 

i'd say these are probably 2 different issues. mine sounds fine in gear

 

I'm getting more and more convinced it's the input shaft bearing...and here have to get this fixed before? I hear it requires replacing tranny...

 

Does your rattling ever stop when the car warms up ? I had similar thing happen to my sentra where a metal cover was loose under oil pan.

 

nope rattles constantly. only during idle in neutral when the clutch pedal is up.

 

I own a 04 6MT since new. From day one I have had the "rattle". When you are at idle you can hear it... sounds like marbles... when you put clutch in the rattle sound goes away...all normal. I had my G 1 day... put in my garage and heard the sound. Went back to dealer... got into 2 brand new 04 coupes on the lot... one just came off truck and both had exactly the same noise... all normal... same on the 350 Z's.... by design. The sound is still there after 80K miles... never had an issue with tranny... sounds is no better or worse.

From My Old Post Years Ago:
Re: Someone settle the infamous 6mt Clutch Chatter

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6MT has a dual-mass flywheel (high performance)... that said read information below (This applied to gear noise (rattle at idle):

The original dual-mass flywheel does one thing very well - exhibits inertia. It is more difficult to change the speed of the dual-mass flywheel, whether accelerating it or slowing it down... that means besides inhibiting engine acceleration to some degree, it also inhibits the deceleration that occurs between every power pulse. The power pulse transition is smoother, therefore no rattle.

A single-mass flywheel is the same sort of design as a solid aluminum lightweight flywheel: a rigid disk of metal, either aluminum or steel. In the OE applications, these flywheels are equipped with a sprung-hub clutch. The sprung-hub clutch "splits thte difference" between the these situations. The friction material (the disk itself) is not "hard coupled" to the hub, but has a springy nature to the assembly. It has a suspension, the springs you see around the hub. What this accomplishes is letting the power pulse couple the transmission's internal parts softly, and then de-couple softly. ("Softly" being a relative term here, it is just a few millimeters of travel, nothing that can be felt.) The net result is the difference between banging two pieces together and gently placing them together.

This clutch design has a center section that is separate from the outer friction area, with a flexible coupling mechanism that uses springs to cushion the power pulse variations. Sounds very similar to the dual-mass flywheel mechanism discussed earlier for a very good reason; the idea is exactly the same, but moves the power pulse variation absorption mechanism to the clutch disk itself.

The issue with gear rattle is that conventional lightweight flywheels retain the car's original solid-hub clutch disk. First, the lightened flywheel has less mass to damp the power pulse variations. Second, there is no mechanism within the solid-hub clutch disk to absorb the power pulse variations. The result is that a conventional lightweight flywheel with solid-hub clutch may create a noticeable amount of rattle. There is simply no cushioning action at all. Note that this gear rattle only occurs at idle, in neutral, with the clutch let out. It is not heard at any other time. Above idle (even just a couple hundred rpm) and the increased frequency of power pulses outpaces the speed at which the components couple/de-couple, therefore no rattle whatsoever.

 

I got my 04 6MT with just about 50k miles on it. It had the same rattle... I traded it off last month with 109k or so on it... it still had that rattle in neutral.

 

Thanks for all the feedback guys. I actually finally got my car back from mechanics today after having a weird rpm drop problem. Turns out the timing chain was off 1 tooth. I noticed that my noisy rattle is gone now too! Two birds with one stone baby! Thanks again.

 

Yea that rattle sound is normal my 04 6mt does the same also..and I also hear it a little between 1 and 2k..but I guess the trans is like that..you should only be worried when u start hearing whining or loud grinding noises