66_Soloracer

I recently purchased a ’92 FX3 ragtop with 133k miles. It is great to get back into the Corvette scene.

My issue, when in neutral there is a noise similar to an alternator whine at idle. Once the clutch is disengaged (pedal pressed), the alternator like whine noise goes away. The whine increases in pitch while in neutral, clutch engaged, as the engine increases in revolutions. When accelerating in 1st gear I can hear the gear rattle and I am not concerned, different noise.

To me, the whine noise sounds like a throw-out bearing. After reading much on-line, I wonder if the noise is the transmission input shaft bearing, or pilot bearing. Or if this is a common noise. The car shifts very smooth with no grinding whatsoever. I have no idea what clutch is installed in the vehicle, it could be original, but I highly doubt it.

Considering the throw-out bearing is no longer available unless in a kit, and I am not sure if the transmission input shaft bearing is a DIY repair accessible from the outside or if it must be created and sent away, nothing seems easy and simple.

Kindly seeking guidance and thoughts……

aminnich

What does the tranny fluid look like?

Deakins

You would have to split the case to R&R the input bearing on the S6-40 transmission. So unless you are pretty well versed with your hands it may not be the best option. Is the whirling noise present at all when in gear with the clutch disengaged? Also, does this care have a stock shifter?

More than likely someone put a clutch in the car and the alignment of the input shaft to the friction disk is off. It only takes a little bit to make them howl. In my experience the aftermarket short through billet shifters make this noise more noticeable as they allow it to resonate inside the cab.

bassackwards

Throwout bearing in clutch

Glenno

I concur!

C409

..... ZF transmissions have a straighter cut to the gears , kinda like the old Muncie M-22 Rock crusher ... it got that nickname because that's what it sounded like ... the black tag trannies were noisier than the blues ... the throwout bearing is not engaged in neutral , only when your foot is on the pedal ... its fine just the way it is ... drive it and enjoy !!! ...................

66_Soloracer

Thank you for the responses!

To address some of the questions:

I have not checked the transmission fluid, I do plan to drain and replace all of the fluids in the next few weeks. I plan to fill the transmission with the BMW oil (I was going to use Red-Line MTL). Engine wise I use Mobil 1 in all my personal vehicles and several have over 200k without any issues, and they do not leak a drop. I have learned over the years one gets what one pays for (but shopping around is encouraged for best values) and shortcuts are more costly in the long run...

I cannot hear the whine when in a gear, too much gear noise.

I am sure I have the factory shifter since it has the reverse lockout pull.

The reason I think I hear so much transmission noise is due to the fact the rubber chassis boot is missing, not installed or is torn. The reason I think this is I also feel hot air when driving coming from the leather shifter boot! I have not removed the shifter console up to verify yet.

I read there are shims between the bell housing and transmission case, which influence alignment. What do these shims look like so I can verify they are installed? What I mean here - are the washer around the fastener locations or actual shims between the case and bell housing? Given what I have found so far in the last couple of weeks, I am hedging maybe the throw out bearing was not renewed or the shims not installed properly or at all.

Is there an access port to verify the flywheel / clutch set-up in an installed transmission?

lt4obsesses

The ultimate source for info and help with these transmissions is Bill Bordreau at ZFDoc.com

My first thought was the release bearing as well. If that is all you need, you can get one from him or Jim Jandik at powertorque. But a t 133K it can be hard to say without any history.

vetteLT193

It is NOT the throwout bearing if the noise happens with your foot OFF of the clutch pedal. These transmissions whine in neutral. It is totally and completely normal. They whined all the way through the run. They made some efforts in the later years to make them less noisy but IMO it didn't work and only resulted in a weaker transmission

If you put your foot ON the clutch and it whines it is a throwout bearing.

Furthermore... the noises are amplified if an aftermarket flywheel has been installed. The aftermarket flywheel is popular because they are much lighter so you put more power down to the wheels and the engine revs quicker.

What you are experiencing with your car has been like that since the day it left the factory. Enjoy it and move on.

66_Soloracer

Thank you all!

I will change my fluids and just keep a watchful ear to the whine and enjoy the moments!

Deakins

The shims are large pieces that cover the entire mating surface between the bell housing and engine, and between the bell housing and transmission. With it being a black tag I wouldn't worry about it. Just my .02

CalvinMD

I like the whine myself..reminds me of my old B model Mack without the extra shifter and them both shaking like hula girls

lt4obsesses

It's hard to say if you have an issue or not over the internet. I will say however that the ZF is an inherently noisey transmission. But the root cause of this noise, is what makes it good in these cars. I have seen alot of posts over the years about clutches, and clutch parts going out. Yet, I have seen very few about this transmission giving up the ghost. So if that noise is the price for durability and performance, I'll pay it everyday.

bassackwards

I believe you have this backwards