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]

Originally Posted by 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

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?

[GOLDCYLON]

Originally Posted by 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?

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.

[Dynomite]

Originally Posted by GOLDCYLON

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."

[Paul Workman]

Originally Posted by S.hafsmo

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]

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.