That's all it is. New number. Nothing has changed.

"The CSC has been failing for 10 years; this seems like a design flaw."
"Well, let's change the part # first and see if that fixes it."

Sent from my SM-G955U using Tapatalk

I wouldn't be surprised to hear the new part number was just some maneuver to avoid reaching a certain number of documented CSC-failures that might trigger a recall.

Got my Z back.. New CSC with new part # 306A1-JK40E, new throwout bearing, and flush the line with GT-R fluid. The bite point is lower now. 1/3 of from the floor. I thought they fk-up. Turned around and had the tech look at it and test drove. I kept think they messed up. But he said everything was normal. Told me to drive it and if I still worried they can adjust it, but said it won't be good for the clutch.

my 2016 base manual does it too
 

My Z is literally at the dealers right now for this exact issue.

Did the replacement parts fix the problem (the whistle)?

Thanks.

transmission replaced
 

After my dealer kept the car and heard the noise for themselves they, under warranty, replaced my transmission and CSC. The dealer called it and 'internal failure.'

In addition to this 'whistle' noise that is discussed in this thread, I noticed a couple other things which have now gone away since this work was done.

First, the original trans was way noisy. I know ppl say the Z is noisy, but with the new trans and CSC, when I let the clutch out, its near perfect silence...near silence. There is still some noise (not the 'whistle' being discussed here) but its much less and now in hind sight I'd suggest this is much more normal manual transmission noise than what I heard with the original trans.

Second, I have read others talk about this but its difficult to describe however if you've felt what I'm about to describe you'll know what I'm talking about. With the original trans / CSC there would be 'cavitation' 'vibration' 'buffering' sometimes when releasing the clutch, from a stop, while in first. Its like the clutch wasn't engaging as it should and the flywheel and clutch plate were glancing off each other rapidly. I initially chalked this up to a sensitive clutch and maybe my own fault at not releasing the clutch smoothly. However since the new trans and CSC I have not felt this and would say the clutch engages much more predictably and reliably. I guess I'm not such a shitty driver after all...

I have not heard the 'whistle' since the work has been done, but I have not let the car sit for longer than over night as I wanted to drive it and verify I'm happy with the work. The whistle generally showed up after letting the car sit for days or really cold weather. So still looking to verify this is truly resolved, but dam they replaced the trans...this better be resolved.

So far, with the little amount of driving I've done, I'm pretty happy. The clutch is more consistent and things feel tight. Getting it into 5th is a little stiff, but the new trans has 100 miles on it, so not even broken in.

Overall, I give props to the dealer. They were accommodating and surprised the hell out of me with the suggestion of replacing the trans. They gave me a loaner car, a Kicks, which was EXACTLY like driving a Z. LOL!!! Not!!!

Now onto a new differential, coil-overs and possibly forced induction.

I also suspect the Transmission. Dealer replaced CSC and pilot bushing. Noise went away initially but Came back a few days later. Not as pronounced, but same type of sound. Hasn't really done it since. Car is now in Hibernation, so we'll see in few more months.

I really couldn't grasp why a CSC would squeal on cold starts. It always has fluid, the actual "Slave" portion Is just an actuator. Leaves only the Bearing portion, which is not lubricated (sealed), but just spins. Correct me if I'm wrong.

While in Idle, in Neutral, clutch NOT depressed, transmission main shaft should be spinning. Noise is there.

Press clutch to floor (idle, neutral) noise goes away. Don't even need to warm up. How the CSC behaves in this manner, is what I don't understand.

Leads me to think Transmission is not getting lubrication where required after sitting for a few days. (oil has flowed away)