Dammit
less than 500 miles on new clutch, TOB, MC, rebuilt diff. Did the work myself, very meticulous, every wire, nut, bolt, clip, etc
Horrible grinding noise when in Neutral and clutch OUT (released)
Clutch IN (pressed) - no noise!
No noise in any gear!
It just started doing this sitting in my garage warming up! 60 seconds into warming up, just sitting in Neutral, clutch released, started making horrible grinding noise. I killed the engine in a hurry let me tell you.
Check the video - tell me what you think. Bled the hydraulics, looks fine, no change.
TOB, correct? not the pilot bearing, it's spinning when clutch is IN (disengaged) and the engine is spinning around the stationary output shaft.

 

Tb or pilot bearing have gone south.

By the numbers.

Free lash/distance between the pressure plate fingers to the back of the bell housing, .124" to 1.50" greater than the distance of the face of the TB bearing (pushed all the way down against the outer spring on the slave), to the face of the torque tube? Hence do not have the TB pre loaded against the pressure plate fingers instead.


Pilot bearing in the flywheel good and the correct size for the front of the torque tube shaft nose (read shaft nose area not all marred to hell, or under size spun worn isntead to cause the torque tube shaft to be loose in the pilot bearing.


Lastly, if you have a tick master cylinder installed, make sure that you have the free lash adjusted correctly. The tick master cylinder can over drive the TB if not adjusted with free play correctly, and force the TB on race to far forward inward against the pressure plate fingers.

So my guess, either free play problem between TB and pressure finger too short and the TB was pre loading all all time to take it out quickly (or just melt is way down on the plastic TB race that is now scrapping off the fingers), the input shaft end of the torque tube was trash or forward loaded on the bearing, which could have been caused by the flywheel not heated and fully seated on the crank surface to start with. Hence the reason that you always check the free gap before you install the drive line to the bell housing.

https://www.corvetteforum.com/forums...uestion-2.html

 

Could be throw out bearing but what clutch are you running and what flywheel bolts, if using arp flywheel bolts they sometimes have to be ground down some to clear the disk if you’re running a twin

 

I think it’s the front torque tube bearing as the root cause.

All of that isn’t rotating with the clutch in. The pilot bearing is probably destroyed (needles all over within the race) due to the torque tube bearing allowing excessive input shaft side load/walk.

 

I agree. Does rpm affect the sound at all?

 

Measurements were done meticulously, according to RPS specs, and they are right in the middle. There is no preload of the clutch fingers on the throwout bearing.

This is an RPS MAMO BC2 clutch, low mile used from another member. Any clearance issues with bolts to the clutch would’ve been immediate, not just happen in my garage one day.

Input shaft look great, I deburred everything, bearings are all new or very recent.

It does have a stock size tick master cylinder. the throw etc. was set up meticulously as well

I guess my options are limited, it’s got to be the throwout bearing or torque tube bearing. Thanks for the help!

 

Wow, that's really bad. My torque tube makes noise so I don't drive the car much but it sounds nothing like that. There is zero avoiding it all coming back apart. Whatever it is should be pretty damned obvious once you get it apart. If you do take apart the tt, be sure to mark how everything is clocked so you can put it all back together the same way.

 

On further thought, TOB only spins when clutch disengaged / pedal IN (correct?) - so this leaves TT bearing or trans input. Noise is coming from clutch area so maybe front TT bearing.

check my logic??

 

Sitting still with the clutch pedal depressed and trans in gear, everything sounds fine, yes? Move lever to neutral - pedal still depressed - sound stays the same? Ease pedal out slowly so that clutch begins to engage and T/T/transmission input shaft begin to spin - but T/B remains preloaded against clutch - any change until pedal is full up or almost full up?

 

I think you're likely right - tearing into it today

yes, yes, and gnarly noise starts when pedal is almost fully up.

 

TOB spins all the time. The coil spring behind bearing pushes it forward.

 

 

And - there it is


bolt backed out of one of the couplers half of them were properly thread-locked and torqued, the other half were finger tight & backing out!
I shoulda caught this when I inspected it a couple months back as part of the clutch job, but there it is.
bolt was rattling up against the bearing. All bearings including the pilot bearing look perfect

One of the PO's had work done by a shoddy shop - they used nice parts but failed the basic stuff in the diff & now the TT.

Good news is it's really minor. Also it took me only about 4hrs to get the drivetrain on the ground, working alone under a set of QuickJacks. I'd rather not do it again though Lot of work for a minor part

everything is cleaned up, torqued and thread-locked, going back in the next day or 2.

thanks for the help guys!

 

yep I was not thinking straight

 

Curious that it didn't make noise while in gear. Think it was just harder to hear while in motion?

 

This EXACT failure happened to me after I rebuilt my TT 3 years ago. It made it 2 or 3 months until I got the same noise after an autocross run and had to tow the car home. My mistake was "reusing" the original nylon thread locking goo. When I put it together the 2nd time I wire wheeled the threads spotless and gave them a healthy coat of threadlocker and haven't had any issues since. Doing it right is helpful lol

 

I never drove it while making the noise. The noise started while idling in my garage, I just tested it a bit with the clutch. Made the noise for a total of maybe 15seconds. it was clear the drivetrain had to come out, so I tore into it.