Transmission noise - DualMass or Throwout?

[S.hafsmo]

On a recent test drive I heard a rather disturbing noise coming from the transmission when the clutch is depressed, and the input shaft has a higher speed than the motor/flywheel.

If I just depress the clutch, there is no noise, but if I rev slightly in neural, clutch enganged, then depress the clutch, a loud rattling/grinding noise appears, and continues until clutch is engaged again.

If it was the throw-out bearing, would it not make noise every time clutch is depressed? Is my dual mass flywheel failing?

A quick and rather poor video of the noise; https://youtu.be/yHi75CXl2lM

[GOLDCYLON]

On a recent test drive I heard a rather disturbing noise coming from the transmission when the clutch is depressed, and the input shaft has a higher speed than the motor/flywheel.

If I just depress the clutch, there is no noise, but if I rev slightly in neural, clutch enganged, then depress the clutch, a loud rattling/grinding noise appears, and continues until clutch is engaged again.

If it was the throw-out bearing, would it not make noise every time clutch is depressed? Is my dual mass flywheel failing?

A quick and rather poor video of the noise; https://youtu.be/yHi75CXl2lM

Hmm sounds like a bad throw-out bearing however I sent your you tube link to the ZF DOC to see what he thinks. GC

[Paul Workman]

Well, in any case it sounds like you're gonna be "in there" soon and find out for sure. But, I'm gonna guess it is the TO bearing or possibly the pilot bushing. (I once has an input bearing on a M21 go bad - sounded pretty bad like the video - but it was worse w/ the clutch OUT than with it depressed, For What It's Worth (FWIW).

Might as well...

...have a new disc on hand when you go in there - sorta mitigates the trouble of going in there in the first place - call it a "clutch overhaul" - freshen everything up at the same time.;)

And...unless the clutch PP or FW surface was burned or worn as result of metal to metal contact/damage to the PP or the FW, there's no concern for "turning" either. The new disc will quickly break-in after a 100 miles of so of use with normal driving. (The Veleo PP is slightly beveled in toward the center. So, you want to avoid any drag race type clutch engagements until the disc has a chance to assume the shape of the disc/FW surfaces.)

[S.hafsmo]

Thanks GC. Qurious to hear what he has to say on the matter.

Paul,
Sure seems I'll be going in there. Really hoping it's not the input shaft, but surely that would make noise (as you mention) when clutch is out as well?
I'm considering to get a clutch kit from ecklers or something. They're about $400 including pressure plate, pilot-, and throwout bearing.
I kinda want a new DM flywheel as well, but then we're in a different league cost-wise. Not that the price is a problem, but annoying if the old FW is still good. Can you tell if it's busted with the tranny/clutch removed?

Anything else one might need in there? clutch fork pivot ball?

[BigJohn]

Woodpeckers them dern woodpeckers again!

[Ronstar]

i have a similar noise (hard to tell from video) in my car. I have a single mass flywheel. let me know what you find out

[BigJohn]

You know with a single mass flywheel and a centerforce clutch my trany sound like a shaking box of rocks when in neutral!
But there is nothing wrong.

[Mystic ZR-1]

So, it's a box of rocks!
I always thought it was your Roy Rogers lunch box
half full of nuts and bolts?
��

[BigJohn]

So, it's a box of rocks!
I always thought it was your Roy Rogers lunch box
half full of nuts and bolts?
��

So you have been looking!!!
Old Roy can really get you out of trouble when needed.
You have your ZR-1 together yet?
We had five cars out in the rain Saturday.

[Ronstar]

You know with a single mass flywheel and a centerforce clutch my trany sound like a shaking box of rocks when in neutral!
But there is nothing wrong.

I'm used to the normal box of rocks. I also have a sound like the OP

[GOLDCYLON]

Thanks GC. Qurious to hear what he has to say on the matter.

Paul,
Sure seems I'll be going in there. Really hoping it's not the input shaft, but surely that would make noise (as you mention) when clutch is out as well?
I'm considering to get a clutch kit from ecklers or something. They're about $400 including pressure plate, pilot-, and throwout bearing.
I kinda want a new DM flywheel as well, but then we're in a different league cost-wise. Not that the price is a problem, but annoying if the old FW is still good. Can you tell if it's busted with the tranny/clutch removed?

Anything else one might need in there? clutch fork pivot ball?

From the ZF.Doc

I replayed the video about twenty times. It sounds like the pilot bushing is
compromised.
Install GM fluted pilot bushing (GM P/N 10125896). WARNING: Applying grease
in a pilot bushing will cause the pilot bushing to fail within the first one
percent of its normal life expectancy. Although very dry looking straight
out of the bag, the oil-lite type pilot bushing is infused with enough oil
to lubricated the input shaft pilot tip for the entire service life of the
clutch. Why not just install a pilot roller bearing instead? When a pilot
roller bearing fails, the input shaft pilot tip will be compromised
requiring removal of the input shaft for pilot tip repair or replacement of
the input shaft.

[GOLDCYLON]

You know with a single mass flywheel and a centerforce clutch my trany sound like a shaking box of rocks when in neutral!
But there is nothing wrong.

Its does. Mine sounded so bad I finally went back to Dual Mass. No amount of sprung hub clutches dampened the noise and in neutral its sounded like the car was going to fly apart. While I miss the faster spin up that the aluminum single hub brings to the HP equation.. For a daily driver the Daul mass makes the car more enjoyable to drive. GC

[Paul Workman]

Paul,
Sure seems I'll be going in there. Really hoping it's not the input shaft, but surely that would make noise (as you mention) when clutch is out as well?
I'm considering to get a clutch kit from ecklers or something. They're about $400 including pressure plate, pilot-, and throwout bearing.
I kinda want a new DM flywheel as well, but then we're in a different league cost-wise. Not that the price is a problem, but annoying if the old FW is still good. Can you tell if it's busted with the tranny/clutch removed?

Anything else one might need in there? clutch fork pivot ball?

From the video, the howling, etc., is typical of a TO bearing, from my experience. When the clutch is let out, the rotation of the input shaft matched the clutch FW/PP. Thus ends bearing noise of either the TO or the Pilot bearing/bushing.

Far as the "clutch kit" goes, it is pretty common to have confusion between the standard Corvette and ZR-1s - far as certain parts suppliers go. My suggestion would be to look to Jerry's Gaskets for your clutch parts. Jerry knows the difference and you won't get the wrong stuff from him.

That said, unless the FW/PP was severely damaged - e.g., during a drag race run, perhaps, or is scored resulting from metal to metal contact between the disc and the FW/PP, chances are heavily in favor of not needing to be serviced/replaced; especially when a new disc is installed as a mater of periodic maintenance, or just freshening the clutch up "while you're in there anyway". (The minor, superficial ridges and grooves on the FW/PP will be assimilated by the new disc within the normal break-in period [100 miles of normal driving city driving]).

Just a thought...

[BigJohn]

Its does. Mine sounded so bad I finally went back to Dual Mass. No amount of sprung hub clutches dampened the noise and in neutral its sounded like the car was going to fly apart. While I miss the faster spin up that the aluminum single hub brings to the HP equation.. For a daily driver the Daul mass makes the car more enjoyable to drive. GC

Mine has been this way since 95 and I am used to it.
Two years ago I replaced both clutch and flywheel.

[Dynomite]

From the ZF.Doc

I replayed the video about twenty times. It sounds like the pilot bushing is
compromised. Install GM fluted pilot bushing (GM P/N 10125896). WARNING: Applying grease in an oil-lite type pilot bushing will cause the pilot bushing to fail within the first one percent of its normal life expectancy. Although very dry looking straight out of the bag, the oil-lite type pilot bushing is infused with enough oil to lubricated the input shaft pilot tip for the entire service life of the clutch. Why not just install a pilot roller bearing instead? When a pilot roller bearing fails, the input shaft pilot tip will be compromised requiring removal of the input shaft for pilot tip repair or replacement of the input shaft.

I install pilot roller bearings with grease and assume they will last a very long time without wear or bearing failure which failures are very rare for the Pilot Roller Bearings.

Some additional information from ZFdoc from previous discussions.......commenting on the correct diagnosis by Marc Haibeck of Pilot Bearing Noise.......

"Marc Haibeck is correct, it is a faulty pilot bushing for sure judging by your description which was very good by the way. To fix this problem, the exhaust, driveshaft, driveline support beam, transmission, bell housing and clutch assembly will have to be removed in order to remove and reinstall a new pilot bushing. What causes a pilot bushing to fail? Grease applied to the inside diameter surface of an oil-lite (oil saturated) pilot bushing is the number one cause for pilot bushing failure. Grease applied in a pilot bushing eventually dries up and clogs the otherwise normally self-oiling pours of the bushing. When installed clean and dry, a pilot bushing should typically provide up to one million release cycles of service whereas when grease is applied, the bushing service life is drastically reduced down to approximately 5000 cycles or less. Typical time to failure with a grease contaminated pilot bushings is around 1.5 years from time of contamination.

The purpose of the pilot bushing is to provide centering support of the input shaft at the far end for maintaining optimal clutch disc to friction surface alignment. With loss of pilot support integrity at the far end of the input shaft comes accelerated wear of the clutch disc friction surface at the outermost region of the disc.

GM has a revised design of the pilot bushing called a fluted pilot bushing (GM P/N 10125896) which has six narrow grooves formed on the inside diameter surface of the bushing which act as scrubbers to prevent glaze from forming on the input shaft pilot tip leading to pilot failure. GM also makes a pilot needle roller bearing of which many people prefer over using an oil saturated brass bushing. The reason I prefer bushing over roller bearing type pilot is because when a bushing fails it usually does not compromise the input shaft pilot tip surface. In the rare event of a pilot roller bearing type failure, the input shaft pilot tip surface is typically compromised requiring disassembly of the transmission in order to replace the input shaft or to have a machine shop install a new pilot tip surface on the input shaft doubling or tripling the repair cost over just replacing a compromised pilot bushing."

[GOLDCYLON]

Mine has been this way since 95 and I am used to it.
Two years ago I replaced both clutch and flywheel.

I was used to it for many years (5). However as a DD its simply got on my nerves. I would not recommend this mod for a daily driver. Track or Sunday car only.... OK

[S.hafsmo]

Truly appreciate the input guys. Give my regards to the Doc!

I think I'll order a clutch disc, throw out-, and fluted pilot bearing. The remaining parts I'll just have to inspect when the tranny is off.

I've replaced DM flywheels with lightweight flywheels before, and won't make that mistake on a DD again. The throttle response is great, but the loss of driveability and the increased rattle just was not worth it to me. For a track car however, it's a no-brainer.

Have anyone tried the steel flywheels from California Clutch?

[conesare2seconds]

Just put a new pilot bushing in 94-0125 because it was greased or lubed in some manner upon assembly. Such a small mistake, so much disassembly to correct. The silver lining was that the backup lamp switch needed to be replaced anyway, and it's much, much easier with the trans out. She got a Hurst shifter as well, another swap that's easy with the trans out. And now I know that the clutch, flywheel and pressure plate are in good kit and won't need to be done for many moons. :)

[S.hafsmo]

maybe I'll replace he backup lamp switch while I'm in there. You wouldn't happen to have the part number for that switch?

I have also stumbled across another issue. I can't seem to find a correct clutch plate. Jerry didn't have any, so if anyone knows of one, or have experience with an aftermarket plate in a stock system, please let me know.

[Racinfan83]

Sounds exactly like mine did from what I can tell. Don't know how many miles your car has - mine had 21,000. I took mine apart and it was the pilot bushing. TO bearing was fine, clutch disc was fine, I had Jim Jandik at Powertorque Systems look at TO and resurface clutch plate. I cleaned up flywheel in the car with Scotchbrite. The ONLY thing I replaced was the pilot bushing - with one of the fluted ones. I added ZF Docs C-beam plates as well. No more noise and everything works great. Jim told me the factory TO bearing rarely goes bad - and a good used factory one is better then the reproductions made in China. So check it out... http://www.zr1.net/forum/showthread.php?t=26185

[S.hafsmo]

Just a minor update on this issue. The tranny is off, and the pilot bearing has approx. 0.5-1mm play on the input shaft, compared to the new fluted bearing. The new one is not a tight fit per se, but has very little play. Minor marks on the outer diameter could indicate that it might have rotated a bit, but it's not very evident.
Everyting else seems to be in good condition.

[Marc Haibeck]

I suggest that you should not use the plain or fluted bronze pilot bearing. We have had problems with them spinning in the crankshaft shortly after installation. I recommend the roller pilot bearing. AC-Delco pn CT1078.

It's interesting to note that GM issued a service bulletin in about 1995 recommending the fluted pilot bearing. Then about nine months later the service bulletin was revised for the roller bearing. That was their final recommendation.

[WARP TEN]

I suggest that you should not use the plain or fluted bronze pilot bearing. We have had problems with them spinning in the crankshaft shortly after installation. I recommend the roller pilot bearing. AC-Delco pn CT1078.

It's interesting to note that GM issued a service bulletin in about 1995 recommending the fluted pilot bearing. Then about nine months later the service bulletin was revised for the roller bearing. That was their final recommendation.

The usual fountain of wisdom. What would this group do without contriubtors like Marc?--Bob

[S.hafsmo]

Appreciate the input, Marc.
I've seen some discussions regarding the use of needle bearing versus the fluted bronze bush, and bought the logic of needle bearing failure could cause input shaft damage. But I'm guessing by your recommendation that no one actually experianced such a failure?

As I've got a bronze bush in hand I'll use it this time, but I'll order a needle bearing. Knowing my luck your predicion will probably come true.