PoloGreen

Hi again (if you've read my recent post about treating leather seats)

I've recently purchased a 95 6 speed and, of course, didn't notice until after driving it for a few days, that when sitting at idle with the car in neutral and the clutch disengaged, I can hear what sounds like a spinning noise coming from the clutch. Once I engage the clutch pedal the noise goes away. Is this normal? Should I be concerned? The dealer I bought the car from is a little ways away so before I head back to see him I thought I'd ask around a little first.

Thanks all.

xlr8nflorida

could be a throw out bearing, but unless it is real bad I wouldn't worry about it.

I have had whine on two of my vettes and nothing ever comes of it. I wouldn't worry about it unless it is really loud.

Vette Ed

polo: my does the exact same thing! maybe the color has something to do with it :lol: my mechanic told me not to worry. :cheers:

bogus

These cars are well known for having a noisy gearbox.

the rattles and whines are not a problem. You do not have anything to worry about. The ZF6 is a killer box!!!! You ain't gonna kill it when doing normal/spirited driving.

Welcome aboard!!!!!! :seeya

offershore

I'm not sure what your saying about the engagement? if you have the pedal down your clutch is not engaged. If it makes the noise then, it would be the throw out brg. If it makes the noise when it it engaged (foot off the clutch) the input shaft brg. is the most likely choice. eitherway it should make no noise! :flag


[Modified by offershore, 11:49 PM 6/12/2003]

PoloGreen

Thanks to all for the feedback. offershore, I guess I was a little unclear with my definition, or lack thereof, of engaged and disengaged. Basically with car in neutral the noise occurs with my foot off the clutch, when I depress the clutch the noise disappears. The noise is not really bad but certainly noticeable. It sounds like something is spinning in there. The bearings that you guys are mentioning, i.e throughout and input shaft, are these big items to fix?

Thanks once again, I appreciate it. :seeya

AGENT 86

Sounds like the throwout bearing is making light contact with the pressure plate. If so your bearing will fail ALOT faster than normal. Check and see if there is any freeplay in the clutch fork. Maybe tired return spring? Worth a look as pulling the tranny just for a throwout bearing is a sad situation. Hope you find the problem !! :cheers:

offershore

Not "to" bad but not cheap either. Find a good trany shop and have them take a listen. They most likely wont even charge you and hearing it in person the'll have a much better idea of whats going on. :flag

Atok

Does it sound sort of like a super charger when you rev the engine in neutral? Contrary to what some people migth say, this is perfectly normal, to a point. I went through the same thing with mine when I bought it (first ZF6). I thought the tranny was going. I called ZF and they sent me to Rockland Standard Gear where I talked to a tech. One of the first questions he asked was "are you a new Corvette owner". He explained what causes the noise and to make a long story short it's the "positive" gear contact of the ZF transmission. What you're hearing is normal gear noise. It will also whine fairly loud in 1st to 3rd gears. Most people don't notice the neutral sound, only us people that like to know every sound our Vette makes and why. You can call Rockland yourself and talk to them about it, they have a 1-800 number on their web page.

If it was a bearing he said I would know it because it would be extremely loud, and it's extremely rare for a bearing to fail on it's own in the ZF. Normally the sychros are the first to fail and normally 2nd and 3rd gear. Also, a bearing will rapidly get worse. Mine hasn't changed in a couple thousand km and the previous owner said it always did it from new. A friend of mine has a '94 with the ZF6, same noise as mine.

I tried changing the oil in my tranny to the Castol stuff. It made very little difference in the noise, but some.

Saying all that, I did manage to get mine much quieter, to the point you can barely hear it. How? Pulled the tranny and replaced the clutch, PP, and release bearing. When re-installing I was careful to align the drive train properly. Cleaned all surfaces ensuring perfect flat fit between engine, cutch housing, and tranny. Then I set the support beam clearances right on spec.

Bill Boudreau (ZF-Doc) told me he's had cases that the gear noise goes away when the clutch was replaced. Maybe due to re-alignment when the tranny is installed?

Read Chevrolet Dealer Service Bulletin Bulletin Number: 77-72-04. For this complaint the first thing the dealer is suppose to do is re-align the drivetrain. You can read it at http://corvetteactioncenter.com in their knowledge base.

Yes, it's a big job to rebuild this tranny. Not something you want to do yourself. If you're thinking about it just take a look at the GM Service Manual and it'll scare you away from the idea.


:cheers:

PoloGreen

Thanks Atok, I appreciate the detailed reply. I'm going to try and catch up with some local club members this week and compare it with others to see if the amount of noise is similar. If I'm worried I'll follow up in more detail.

Thanks again :cheers:

Patrick96LT4

Relax, it's normal. Both my 96's did/do the same thing. :rofl:

Voltech_LT4

mines at the tranny shop right now for this problem... they have had my car for 3 weeks now. I just had a new clutch, flywheel and tranny installed last June and although the noise hasnt gotten worse, they said that when they pulled the tranny that the clutch was destroyed. Luke Clutch is replacing the flywheel, but no word on the clutch yet. I will be :mad if they try and make me pay for the clutch or anything else... its still under warranty. They sent the clutch/flywheel to luke clutch about 2 1/2 wks ago for warranty investigation to make sure it wasnt caused by "abuse". This pissed me off in itself because I dont beat the crap out of my car. The clutch should last alot longer than 9 months, even if you did beat the crap out of it. I was told the same things.... throwout bearing, input bearing, maybe synchros.... we still dont know yet. I'll let you know when I find out. :mad

Voltech_LT4

The tranny place called me today... Lucas clutch is going to cover the warranty for a new dual mass flywheel and a clutch. They said the clutch was defective. I pray the noise is gone when it goes back together :blueangel: I'll let ya know... they said my car will be back together by the end of the week. Its been 4 weeks now! :mad

Patrick96LT4

That may be, but here are two things to note:

My first 96 LT4 had 19k miles on it when I got her, and it made this sound from start. I thought something was bad until I heard my friends 96 CE and it did the same thing, he had less than 10k miles at the time.

The I bought the GS, and it had 11k miles on it. Guess what? Same noise.

I can't imagine all of these cars had damaged/broken parts. I just think the ZF6 is really noisy when the clutch is out.

Cal Vette

Not to worry, mine has slight noise too. I was told by many, not to worry, just drive it and have fun! How many miles do you have? :cool: :chevy

Voltech_LT4

makes sense, but when they yanked the tranny and saw the clutch, it was destroyed along with the flywheel. They sent it out and made it out like it was abuse on my part, but I told them it was making a noise even after the new tranny was put in and upon testing they found the clutch to be defective. Im glad I brought it to the shop, but I have to tell ya, I was :mad when they even considered it being abuse on my part. I drive it fast quite often, but rarely dump the clutch or beat the crap out of it... its highway driving mostly. It had 14k miles when I bought it a year and a half ago. It makes me a bit uneasy to hear noises in a car I spend so much cash on. I love the car though, its a beast. I hope your right Patrick. :yesnod: :cheers:

Atok

:iagree: :iagree: :iagree:

Exactly what I was told, the ZF is a noisy gearbox. Gotta pay the price for performance. Careful driveline alignment definitely helped mine in neutral but the sound is still there.

:cheers:

PoloGreen

Cal Vette - the car has about 38K Kms on it (about 24k miles). The more I read through this post the better I feel, I think for now I'm going to drive her and keep on eye on her and chalk it up to being an average ZF6 tranny.

Thanks to all for the feedback! :cheers:

Red Tornado

I have two '90s with ZF6, one has 53k miles, the other 63k. They are both a little noisy with the clutch engaged, dead quiet otherwise. Just my .02 :seeya