Throwout Bearing Play

[Shizap]

Hey Guys,
I am trying to figure out why my recently installed SPEC clutch has so much shuddering/chatter going into 1st and reverse. Could the play in the throwout bearing be the source of my problem? I linked a video of the new setup vs the old. There is much more play in the setup SPEC sent me....
I assume that this wouldn't be a problem because the throwout bearing slips over the input shaft, but now I am not so sure.
https://www.youtube.com/watch?v=CvyMp845IzA


Thanks,
Scott

[1991 Corvette ZR-1]

It should not be an issue. The important idea is the retainer will ensure the TB bearing stays mated to the plate fingers. I just did a clutch change recently and same loose look as yours. All the new ones are like that. No issues and runs quiet. If you have not already, I would recommend a fluted pilot bushing to go with your new clutch.

[Shizap]

Yeah, that is what I figured. It is good to hear that yours had the same play and works correctly. That's one less thing that can be my issue.
Thanks,
Scott

[wfot]

There are 2 different diameter input shaft tubes
90 - 92 are wider
93 - 95 are a little thinner.
the 93 - 95 won't go over the 90 - 92 input shaft however, the 90 - 92 will go over the 93 - 95 but will have "slop" and be able to rock back and forth.

Also, I have heard that there needs to be a decent break in period before the chattering goes away. IE; 500 miles of city driving.

Does it hang up shifting/chatter once the car is rolling? or does it chatter just from a stop?
John

[Corvette95]

I threw my SPEC kit in the garbage after 3 installs and removals for shudder.

[gtcollins@maxnet.co.nz]

Clutch chatter when you are just engaging the clutch can also because from a clutch plate that is bent not running true this can happen when you install the gearbox and it hangs down on the clutch plate before you bolt the gearbox up

Glen

Sent from my SM-G998B using ZR-1 Net Registry mobile app

[Shizap]

Originally Posted by Corvette95

I threw my SPEC kit in the garbage after 3 installs and removals for shudder.

I think this is my exact issue. I installed a new Spec clutch kit and a resurfaced aftermarket flywheel, and the result was I had tremendous shudder going into first and reverse.

After the issue was only getting worse the more I drove it, I decided to pull the transmission again to see what might be wrong.
- I ended up replacing the Aftermarket single mass steel flywheel (incase it was resurfaced wrong) after seeing hot spots on half of the flywheel and half of the pressure plate surfaces.
- I bought a new Clutch Disk incase it had excessive runout.
- I sent the same SPEC pressure plate back to SPEC to be "refurbished" before reinstalling (it was a nightmare dealing with them by the way)

After doing all that I have the exact same issue. All signs point towards it being a bad Spec pressure plate. I don't think they did anything at all to refurbish it, besides clean up the surface.


If I had known how bad Spec was before going through this process, I would have bitten the bullet and gone with the Ram conversion system to begin with. Now I don't want to drop that much money without knowing the exact issue. I am going to try this one more time with a different pressure plate (not a Spec). Hopefully third time is a charm....

[1991 Corvette ZR-1]

So ZF Doc aka Bill Bourdeau has a service in which you can send him your pressure plate and he can make sure it is correctly set up, so it has proper engagement of the disc and not lop sided. If I remember correctly, he mentioned the parent company that owns Valeo has a monopoly on the style of pressure plate made for pull type clutches for C4 Corvettes and they do not care about tolerances and accuracy. So no matter where you get the pull type pressure plate from, if it is not NOS OEM, it is coming from the same manufacturer slapping them together. So the SPEC plates are very likely the same pig, just wearing lipstick - pretty blue paint.

If I were you, I would take the time, reach out to Bill or strongly consider the push type conversion.

[Shizap]

Originally Posted by 1991 Corvette ZR-1

So ZF Doc aka Bill Bourdeau has a service in which you can send him your pressure plate and he can make sure it is correctly set up, so it has proper engagement of the disc and not lop sided. If I remember correctly, he mentioned the parent company that owns Valeo has a monopoly on the style of pressure plate made for pull type clutches for C4 Corvettes and they do not care about tolerances and accuracy. So no matter where you get the pull type pressure plate from, if it is not NOS OEM, it is coming from the same manufacturer slapping them together. So the SPEC plates are very likely the same pig, just wearing lipstick - pretty blue paint.

If I were you, I would take the time, reach out to Bill or strongly consider the push type conversion.

Yes, I?m aware that all the pull type clutches now made for C4s are made from the same parent company. Unfortunately, it is near impossible to find a NOS Valeo plate. Did you end up sending your pressure plate off to ZF doc for this service?

[1991 Corvette ZR-1]

Originally Posted by Shizap

Yes, I?m aware that all the pull type clutches now made for C4s are made from the same parent company. Unfortunately, it is near impossible to find a NOS Valeo plate. Did you end up sending your pressure plate off to ZF doc for this service?

I did not. I actually found out about if from him the night I was installing the assembly into the car. Impatience and rolling of the dice and all that. Also, I had just received the flywheel and plate back from a balance job done by Marc. I did not want to risk compromising the balance job if Bill had to level any of the pressure plate feet. Thankfully, all has been quiet and well with smooth engagement.

If you are willing to wait a week or so, give him a call. If it were me, I would. Dropping the trans is no fun, even during the winter months.