About 10k miles ago I had a bad TO bearing -it had the continual squeak noise until you pushed in the clutch. I had never replaced one, but decided to do it in my garage and since the car had about 85k miles, I also decided to replace the flywheel, pressure plate, clutch, pilot bearing and TO bearing ... do it all one time.
Last summer I periodically had growling with the clutch peddle in and everyone said it was the TO bearing ...again. But it would be intermittent and sometimes not happen for days.
I decided to have it done this time by a great local garage. They did it last week and everything was fine. Today we had a nice warm day, so I figured I'd get some seat time in the Corvette.
I had some fun, but got back to the house and pushed in the clutch and my growl is back -just like before, I can pump the clutch a little and it stops, for a bit, but will come back after a while.
What is wrong with this TO bearing -or is there something that is being missed?
This is a great car, but man.....
Can anyone give me a clue -is it just a 4+3 problem?
One thing that I did find out when I did the work the first time is that the transmission is not original -it had an 1985 date code on it -can that be a problem?

 

just bumping -anyone have an idea?

 

Each time you had the TOB out, did you confirm if it was bad? I'm no expert but if the TOB bearing is wearing quickly it could be because it is being held down against the pressure plate by the clutch fork while the clutch is engaged (trans spinning). Basically the pedal / hydraulics may not be fully releasing. I'd start by investigating the clutch hydraulics, fork, pivot and pedal before tearing into it again. Also the spring on the clutch fork needs to be inside of groove on the TOB, I'm not sure what happens if the spring is on the outside but I thought I should mention it since the tech bulletin that came with my Luk clutch kit mentioned it.

 

That same thought occurred to me as well, Wazz. Double-check your hydraulics along with making 100% certain that the fork is working/pivoting correctly.

Later,

Lee

 

Thanks.
When I changed the TO bearing 10k miles ago it seemed real loose.
I had it done this time by a local garage and they were the ones that diagnosed the problem as the TO bearing, even though to me it was a totally different sound -just before replacing, and now after the mechanic changed the TO bearing last week, it is a low growl.
someone said that it could be the pilot bushing?
My hydraulics are both relatively new -replaced them both last year when I had the soft clutch peddle problem.
I thought about how the TO bearing was installed, but again, this time it was installed by a mechanic at a local garage and last time it was installed by me.

 

Weird, once in a great while something happens to my car (not sure what provokes it..) but my 4+3 z51 will also get that growl... kinda like a grinding/growling noise like there's something else attached to the flywheel making noise. During these moments of growl, the car can get REAL pissy trying to get into 1st or reverse. I notice that when shut down and restarted some time later it's 'fixed' itself.

 

Yes, mine does everything just like you have described!
Anyone have an idea what these symptoms are indicating?

 

It sounds like you hit all the usual suspects. Does the sound occur in neutral with the clutch pedal released? is it possible the noise is coming from the trans input shaft bearing?

 

No, the noise is not there when in neutral with the clutch released.
How would I further evaluate the input shaft bearing?

 

I think if you had a transmission input shaft bearing going out you would hear it when the clutch is engaged. If you ease into the clutch pedal without actually releasing the clutch, you will load up the the TOB and not the pilot bushing, that would confirm a bad TOB, but would not determine why it failed. If you find the noise starts only after the clutch is fully released, it could be a bad pilot bushing. Since it sounds like your shifting is notchy, that means something is grabbing the input shaft when the clutch is released, so either your clutch is not releasing completely or the pilot bushing is bad.

For clarity, clutch is another word for grab, so when I say clutch is engaged, that means it's making contact with the pressure plate flywheel and therefore the input shaft spins with the engine.

Clutch released means that the clutch is no longer "clutching" or grabbing the flywheel and the flywheel and input shaft can rotate at different speeds.

 

I'm pretty sure that mine does in fact still grown in neutral w/ the clutch released but not positive...

 

Not preaching...just hopefully adding information to help.

From experience.

BOLD words are not me yelling....just to emphasize importance.

TEST 1: When the transmission does not allow first gear to be engaged WITH the engine running...SHUT off the engine and then TRY IT WITHOUT the engine running. If the transmission will go into first gear...then this is telling me that the pilot bushing is the culprit. This takes out any hydraulic issues. And this is assuming that the shifter is set-up correctly and the linkages were checked and all OK.

This is due to the input shaft of the transmission is still rotating with the engine while it is running...but when the engine is not turning...the transmission will allow first gear to engage.

TEST 2: Check your crankshaft end play. I have had a Corvette a while ago that had .065" crank shaft run-out or end play. And it was so excessive that the counter weights of the crankshaft were beginning to lightly scrub against the main bearing caps. Riding the clutch pedal may not damage to the clutch disc...but it does wear out the thrust bearing.

As mentioned in an above post. The front bearing can be a partial issue. (not preaching) Remember...this bearing and the pilot bushing need to be RIGHT in order to keep the shaft true and not 'wobbling'...so-to-speak. YES...I know that this shaft is not tight ...and does move...but if it is excessive...this may be part of a problem.

AS mentioned in an above post. Properly clipping installing the throw-out bearing in the clutch fork is important and the clutch fork needs to be looked at very carefully.

I am picky when I get a throw-out bearing. Due to many parts being butchered by the 'bean counters' of the companies that make them. I do not assume that what I get it worthy of me putting it in. I have had new throw-out bearings being so 'cheesy' that they make a good paperweight.

The pilot bushing is also suspect. If using a solid bronze bushing....you need to make sure that it does not have iron in it.... so...a magnet will not stick to it. I have seen the iron impregnated pilot bushings damage and seize up on the input shaft tip. I know many like using the roller bearing design pilot bushing. I do use the roller design pilot bushings when it was installed from the factory. I have seen them fail.

Clutch fork and pivot stud. Worth taking a good look at.

If on both cases...if the noise is not there right when it is cranked up and all parts cold....but the noise comes on later after it has been driven...then I would have to look at what parts that are moving and when heated can change. Many have been listed above.

The 1985 transmission is highly unlikely the issue.

And...I am sure that the bore concentricity was checked and also the parallelism checked also. It is a very helpful to the clutch function, vibrations, etc...and many do not check these.

DUB

 

Well in my situation, when I shut the car off and restart it the grinding issue goes away, and clutch goes back to normal in terms of shifting gears. But awesome information, thank you so much.

 

Thank you very much for taking the time to get me some things to look at!

1) No problems shifting into first with the engine running, unless I have the growl -but even then it still goes in but does a slight gear ding as it goes into gear.
2) With the holidays I haven't had a chance to do this testing.

Regarding the contaminated pilot bushing cause. You indicate that the bushing can seize if contaminated. This was replaced about 10k miles ago when I replaced the TO bearing the first time. If it got a little contaminated when I installed it -could that be just getting worse and the grinding is like it just starting to show the signs of seizing?
As mention, when I get the grinding when I first push in the clutch, I can most often get rid of it by leaving the transmission in neutral, engine still running and letting off of the clutch peddle and then pushing it in once or twice.
Then it may go a week without it happening again.

I was reading an article from 2012 about the 84 4+3 and one of the weak links the brought up was a "clutch thrust washer that was prone to spin when it needs to remain stationary" -they indicated this was corrected in 1985. I'm wondering if this thrust washer spinning could cause a growl noise??

 

This makes me think pilot bushing too, as others have talked about.

One more thing to look at if trans is out w/regard to TOB/fork etc is the front bearing retainer, where the TOB slides. It can wear and create havoc with clutch release and engagement

 

Did the noise exist before you replaced the flywheel? If you can, get the car in the air, try to duplicate the growl, use some form of a stethoscope and listen to the 4 speed portion of the transmission. What you may be hearing is the countershaft in the 4 speed spinning and making noise. The couther shaft is always in contact with the input shaft gear, do you have the proper lube in the 4 speed section?. Just some wag. The notch shifting and having to neutral it and then getting a smooth first gear shift leads to the clutch not fully releasing or the syncronizers starting to fail. This of course assumes everything else is in order. Again, others have offered very sound observations.

 

I never wrote about a contaminated pilot bushing. I wrote about the pilot bushing be a bronze one that is NOT magnetic...because many pilot bushing have iron in them now...and can cause a problem. If it gets damages during transmission installation...it can cause the transmission not to go into gear when the engine is running....but will when the engine is off.


As mention, when I get the grinding when I first push in the clutch, I can most often get rid of it by leaving the transmission in neutral, engine still running and letting off of the clutch peddle and then pushing it in once or twice.
Then it may go a week without it happening again.

I was reading an article from 2012 about the 84 4+3 and one of the weak links the brought up was a "clutch thrust washer that was prone to spin when it needs to remain stationary" -they indicated this was corrected in 1985. I'm wondering if this thrust washer spinning could cause a growl noise??[/QUOTE]

Check your crankshaft end play...it is somewhat easy to do to take it out of any possibility of being 'suspect.

Call these guys.....I use them and they know their stuff.

http://www.5speeds.com/dne.htm

DUB

 

Sunday I planned on spending some time trying to follow through on some of the suggestions for further evaluating the "growl".
I started the Vette and held in the clutch with the transmission in neutral and let it run - it was fine for about a 15 seconds and then gave a little growl.
I let it out and then pushed in the clutch again and it growled after a few minutes.
I pushed in the clutch and let it out and pushed it in again and no growl again, so I held in the clutch for at least 3 minutes and no growling with the transmission in neutral and car idling at about 800 RPMs.
Still holding in the clutch, I increased engine to about 2k RPMs for 30-40 seconds and the growl came back but would go away with lower RPMs.
At that point, with the engine still running, I pushed in the clutch and shifted 8-10 times from 1st to reverse and it was fine.
I did one more test holding in the clutch, transmission in neutral, and holding it at about 2k RPMS for 30-40 seconds and no growl -I repeated this about 3 more times and no growl.
Yesterday I drove the Vette about 12 miles of stop and go traffic and never had one single growl and the transmission seemed smooth as silk.
It seems that I need to keep driving it and if it stays OK great.
If not, it will be easier to find if it gets worse and consistently growls?

 

Talk about putting your thrust bearing to the TEST. DAMN! You are aware that when you have the clutch pressed in and holding it....all that pressure is on your thrust bearing....and if it has not been checked from my previous posts to you...you are shortening its life....thus increasing teh crankshafrt run-out...which is an important factor....and was written in POST#12.

Holding in on the clutch is a bad habit...but it is your car.

I HONESTLY hope that your crankshaft run-out is still in specs.

DUB

 

Ok, I did not think that through and looking back it was not too bright.
I am going to Harbor Freight today to pick up a dial indicator.
Because I don't want to mess up again;
I have never checked the crank shaft run-out, but doing a search, I read that after setting up the dial indicator, I "pry" the crank back and forth.
It seems that the easiest access to the crank will be from underneath at the harmonic balancer?
Or is there a better place to pry it and a recommended method?
Thanks for your patience -I am definitely learning something new.