Hi everyone,

First time poster here. I have a 2007 with a 6mt that has started making a lot of noise in 1st gear. The car only has 40k on it and I'm the only owner. When I decelerate there is a REALLY loud whine coming from 1st gear and I don't hear it in 2nd and above, those gears seem to have the normal whine.

- my friend put the car On the lift with me inside and asked me to replicate the problem while he was underneath - not a single whine.

- I did a high rpm decelerate in 1st gear on the street and it was whining so I dropped it in Neutral and the noise disappeared.

This isn't adding up. Is the issue the gearbox, differential or what? The car never pops out of gear or has grinded. Any help is much appreciated. Thanks!

 

Did the noise you hear begin when it became colder outdoors?

 

I would say it did get louder with the cold but I didn't have this issue during previous winters since I owned the car

 

Welcome. First, from what you're describing, it sounds like this "REALLY loud whine" only occurs under load. So the drivetrain is attempting to accelerate or deaccelerate with the full weight of the Z and any passengers onboard. Does this happen only after HARD acceleration and backing off, or is it present when there's only light acceleration (before shifting gears)?

What brand and type of gearbox lubricant are you using? When was it last changed?

 

Thanks for the welcome!

Even under light acceleration in 1st gear ill hear it and it'll make a "chugging" noise too along with the loud whine. But under hard deceleration it's crazy loud. I can't hear it under hard acceleration bc engine noise takes over then. I'm using the OEM fluid and it was changed 10k ago.

 

Have you checked the actual fluid level in the tranny? Does it seem to getting worse?

 

I haven't checked the fluid since it was changed 10k ago and I know tranny fluid doesn't get consumed the way motor oil does. It doea seem to have gotten worse.

Could it be a bearing issue or something internal in the transmisson? Like I said, accelerating and decelerating in 1st with the car on the lift didn't yield the noise. My friend was under the car in hopea of tracking where the sound would be coming from but didn't hear a thing.

 

That happened to mine since I got it new. It handled all the power and abuse and never broke on me (I mean the tranny of course) lol. You should be okay.

 

I would accept it as normal if my car did this from day 1 but it didnt.

 

I'd rule out the easy problems first. Get the Z up in the air and LEVEL. Pull the tranny fill plug and see if the fluid is at the same level as the hole (should seep a little).

If that's not it, the next thing will involve pulling the tranny and checking items like the throwout bearing, pressure plate or other internal components. Could also be an internal gearbox problem, but that's getting ahead of yourself.

 

Mine makes that noise in first gear It started doing that about three years ago), but only when it's cold outside. After driving in traffic a couple of minutes, the sound goes away.

 

So a little while ago I go in my car to start the car and the dreaded clutch pedal sunk to the floor with no pressure. Car wouldn't go into gear and there was no clutch fluid in the reservoir. I had it towed to my friend's shop. It most likely is either the master cylinder or the slave I'm guessing.

Could this be related to the 1st gear whine?

 

I am surprised no one brought this up, but isn't 1st gear and reverse gear whine normal because they are straight cut gears instead of helical for extra strength?

 

Good point. That would certainly explain the noise from first and reverse gear (something I experience).

The transmissions in racing cars have straight cut gears, and they are very noisy.

Do straight cut gears provide more strength (than helical gears)? I thought that straight cut was used mainly for its versatility than its strength.

 

But that doesn't explain why it only recently got this loud. It was quiet before under those conditions.

 

^^ Google straight cut gears.

Notice that this type of gear can become noisy when it wears, and wear is typical of this gear type.

 

Thanks I'll google it. Does the wear ever get so loud where the gear would pop out on its own? I suppose if the noise is the only thing that'll get louder then I can live with it.

 

Before we take this too far OT, let's not clutter this site with misinformation. First gear in our six-speed trannys use a triple cone syncronizer, not a straight cut gear. Having driven racing transmissions in Nissan GT cars, their straight-cut gears cannot use syncronizers. Instead, those trannys use dog rings to help transfer power. They can be quite noisy if you don't match RPM to the input shaft speed.

The sound you hear when downshifting into first in a Z33 (not using heel-toe technique) is the sound of the syncronizers trying to match the speed of the tranny with the engine. That's why I recommended the OP check the fluid level in the tranny case. If it's low, the syncro may not function properly and could get damaged.

 

Thanks for chiming in.

 

Thanks for the info. The car is at my buddy's shop and he will take a look at the oil level for the tranny as well as what the hydrolic issue could be regarding the clutch (no pressure and car doesn't go into gear). I wonder if this could be related to the whine. Ill let you guys know what the issue is.