Hey guys, I just wanted to say first that this is my very first post on here but I’ve always googled questions about my G and you guys have never failed to answer all my questions on other threads that people have posted.. so thank you!

Aside from that, I bought my dream car (a G35) last August and it’s been nothing but amazing up until the past couple weeks. My mechanic was working on my car earlier and noticed there was a ticking sound coming from under the hood which could be a sign of something wrong with the transmission. Long story short, work and life came up so I haven’t had a chance to check up on it.

Well, just yesterday I’m on my way home from work and the clutch goes NUMB. Numb like it’s not feeling like it’s even doing its job anymore. In addition, just lightly pressing on the clutch would create a loud squeaking noise until my foot was off of it. The clutch also would not come up on its own, I had to put my foot underneath the clutch and kick it back up.

Being that (I will admit) I don’t know too much about the engine and mechanics of cars since I just recently got into it, I wanted to ask if any of you might know what this could be or if you have any suggestions before I take it to a shop and have them say some bs like I need a whole new tranny if they know I don’t. Has this happened to you before?

Thank you guys so much )

 

Welcome!
Most likely your clutch Slave cylinder has failed?
I had that problem on my previous 06 G35 6speed at 92.2k miles. It was replaced at the dealer under warranty.
With a now almost seventeen year old vehicle, In addition, most likely the clutch master cylinder may also need rebuilding along with new clutch fluid.
You can obtain quotes from your local Infiniti dealer as well as from a few independent transmission shops.
Good luck

 

Loud noise while the clutch is depressed and a soft clutch that doesn't return is all the signs of a failed throwout bearing.

How many miles are on the car, if it's over 100k miles you should just replace the TO bearing, clutch, flywheel, and pilot bushing. The tranny has to be removed to access the TO bearing which is typically a 10 hour labor job to remove/install, that will be a significant amount of money in labor so typically you would replace all the wearable components while it's off if there is enough miles on them.

The mechanic can inspect the throwout bearing by removing the clutch slave cylinder (60 second job, it's just 2 easily accessible bolts) clutch fork rubber boot and using an inspection mirror and flashlight to look up into the transmission bellhousing to see if components have actually broken but the loud squeaking is pretty obvious.

When you press the clutch it puts pressure on the TO bearing which rides on the clutch pressure plate, the bearing is now spinning at the same rpm as the engine and when the bearing dies it makes that horrible screeching. When you let off the clutch pedal there is no more pressure on the bearing and it basically just floats in place right in front of the clutch pressure plate.

I'll attach some pictures so you have an idea what all these components look like and how they mate to one another.

 

This post will be picture heavy but will give you an idea what all these components look like and how they match together, first photo has a clutch, pressure plate (red with the metal fingers), flywheel, and a throwout bearing, and small brass pilot bushing all laid out. Ignore the plastic splined alignment tool, that doesn't stay installed in the vehicle.





Next is a picture of the clutch fork with a pivot ball (the little threaded stud) already in it, the pivot ball screws into the transmission bellhousing. Also attached to the end of the clutch fork is the carrier for the throwout bearing. The rubber boot fills the gap where the clutch fork goes through the transmission bellhousing.




Next is a picture from inside the bellhousing with the clutch fork removed, you can see the window/hole in the bellhousing where the clutch for protrudes outside. The pivot ball is installed into the bellhousing, it's that copper colored piece, the color is the grease/lubricant that is applied to it.





Here is a view from outside the transmission with everything installed but with the rubber boot removed so you can see into the bellhousing, the clutch slave cylinder is that corrogated rubber piece that is attached to the end of the clutch fork.





Here is a the throwout bearing, an old compared to a new one that has been reinstalled onto it's carrier housing, this is the same carrier that was shown in the previous picture attached to the clutch fork.





Next is a view of just the clutch fork installed into the bellhousing. You also see it fits around the transmission input shaft which is splined on the end.






And this is what it looks like with the throwout bearing installed back onto the input shaft of the transmission. Ignore the carrier to fork retaining spring that is installed backwards. The carrier bearing rides on the smooth section of the transmission input shaft housing and as you press the clutch it goes in/out along that shaft.





Now we move along to the engine side, first is a picture with just the flywheel installed. Your OEM flywheel looks different from this one, I was installing a lightweight flywheel which is better for performance but a little less "user friendly" and a lot more noisy (clutch chatter). The brass pilot bushing is right in the very middle of the flywheel, it's actually installed in the back of the crankshaft and the flywheel bolts to the engine crankshaft. Once the transmission is reinstalled the very tip of the transmission input shaft will fit into the pilot bushing which stabilizes the transmission input shaft.





Next component is the clutch friction disk, it has an alignment tool installed into it to hold it in place, once the pressure plate it bolted on the clutch will be sandwiched between the flywheel and pressure place with several hundred pounds of force so you use the alignment tool to make sure everything is in the exact location before clamping it together. The clutch doesn't bolt to anything, it floats in the middle of the flywheel and pressure plate, the transmission input shaft will go through the middle of it once the transmission is installed. The flywheel bolts to the engine, the pressure plate bolts to the flywheel so those two components rotate at the same speed as the engine, the clutch attaches to the splines on the transmission input shaft so it rotates at the same speed as your transmission.





Now we have the final component, the pressure plate, it bolts to the flywheel and the clutch is clamped between the two. Notice all the metal "fingers" of the pressure plate, the throwout bearing presses against these and pushes them in, this causes the other side of the pressure plate to release pressure off the clutch so it can spin freely between the pressure plate and the flywheel.

First photo is a picture of the pressure plate so you can see the fingers, they pivot out near the outside of the plate. If you look closely you can see the clutch friction plate in the very center, only it's metal hub is visible with the internal splines that will mate to the transmission input shaft.





And here is a picture of the pressure plate bolted to the flywheel.





And one final picture of the other side of a pressure plate, it is a smooth metal surface just like the flywheel. As the fingers are depressed the metal plate is retracted backwards a slight amount which takes all the clamping force off the clutch so it can spin freely.





So how it all works, you press the clutch, the slave cylinder extends it's little plunger to push on the clutch fork outside of the transmission, the clutch fork pivots on the pivot ball and pushes the throwout bearing onto the pressure plate with enough force to push the pressure plate fingers in about 1/2" to 5/8" which releases the clamping force from the face of the pressure plate.

The throwout bearing is spinning with the same rpm as the engine while it's pushing against the pressure plate since that plate and the flywheel are bolted to the engine crankshaft and spinning at the same rpm as the engine. The clutch is floating between the two when the clutch is pressed, the clutch is clamped between the two when the clutch is released. The transmission input shaft goes through the center of the clutch friction plate and they are mated together with a splined shaft.

When the throwout bearing fails it's common for it to make a lot of noise but only while you have the clutch pressed in which is making it spin.

This is LIKELY the sound you're hearing but there's always a chance that it's something else, possibly a component that is actually broken not just worn. This is the best diagnosis I can give without actually troubleshooting the car in person.

Hope this helps.

 

Also, apologies if you already know how the components of a clutch function.

 

Wow, thank you both for the advice. And thank you cleric for the detailed posts! You gave me such a better understanding about what’s going on under the hood and those pictures are greatly appreciated! My car has been sitting on the street for two days and I just started it back up again to hear it. I am currently waiting for the tow truck to arrive. Not sure if this helps but here is a video of what the clutch sounds like when it’s engaged. https://imgur.com/gallery/7Z6PMqd

 

Yeah that's definitely the throwout bearing, that's EXACTLY the sound it makes. Normally it's not spinning but every time you touch the clutch pedal it presses up against the fingers on the pressure plate which is spinning, that makes the front of the throwout bearing spin.

They will eventually fail from normal usage but TYPICALLY when the TO bearing fails before the clutch it's usually because of improperly using the clutch. When you are sitting at a red light never sit there with the clutch pedal depressed, instead you need to shift to neutral and release the clutch. Otherwise the throwout bearing is sitting there spinning for up to several minutes, it's only meant to be engaged in short intervals of up to a few seconds.

Also never EVER drive around with your foot resting on the clutch pedal, even the slightest pressure causes the TO bearing to start engaging on the pressure plate.

Don't be surprised if you also get a diagnosis that the clutch slave cylinder and clutch master cylinder need to be replaced. Every one of the clutch components has a typical lifespan of 100k-150k miles, some folks that are very easy on the clutch can get upwards of 200k out of the stuff but a sports car typically goes through clutch components due to aggressive driving.

 

Thinking back now, I never even realized I was doing that out of habit! I often leave my foot on the clutch just when I’m chilling in a gear or even neutral just for no reason whatsoever. That’s probably part of the reason why I’m having this issue now added to the fact that the car’s got about 143k miles on it and the clutch has never been replaced.

Welp, my G is in the shop now and my mechanic said he’ll be giving me a diagnosis soon. I’m hoping your diagnosis is correct and it’s just the TO bearing / master / slave cylinders so that -hopefully- I can save myself some money.

Thank you so much for the help!!

 

Unfortunately I suspect they're going to recommend a new flywheel, clutch, pressure plate, pilot bushing, and throwout bearing. That is about $800 worth of parts not including labor which is typically a 10 hour job at whatever your local rate is (typically about $100/hr). Additionally you SHOULD replace the clutch master and slave cylinder any time you replace the clutch because those components have about the same life expectancy and when they fail they can actually ruin a brand new clutch.