Clutch Fork Failure Analysis Prediction?

[efnfast]

So I assume this is not the same fork used in all C4's?
Is this ZF unique to our ZR-1's?

[QB93Z]

Originally Posted by Schrade

Kind of confused here about 'welding' / 'preventative' measures...

OP asked about Failure Analysis Prediction, and I think the discussion would have ended when someone mentioned Magnaflux (besides visual inspection)...

I agree that magna flux inspection would be an excellent test to identify potential failure. But, it is not a test I can do in the garage while I have a clutch apart for some other reason.

My conclusion is that the fork is not a part that "wears" down like a brake rotor. It is either a good clutch fork, or it has failed and you can't operate the clutch. I guess there could be a noticeable bend before it fails.

Jim

[WVZR-1]

Originally Posted by Dynomite

Good question?

I have a 90 (L98) with ZF S6 40 trans also and I expect that the clutch fork is identical but am not positive.
I would never try to weld or stiffen a clutch fork (the failure is an anomaly) and the heat treatment of the original is unknown.
I have seen clutch forks on Ebay as well as complete bell housings with clutch forks installed.

Clutch forks do have three wear points (fingers at the throwout bearing, pivot, slave cylinder plunger) all of which should be greased a tad upon installation.

All C4 ZF's use the same part #'d clutch fork! ALL!!

[cvette98pacecar]

Originally Posted by scottfab

I'm not a welding expert (have welder will make a mess) but have seen skilled welders lay down a bead of high strength steel (E1203X) that is low profile. (profile set by the welder). Such steel is MUCH stronger than the original steel. (120,000 psi).
Not sure this idea would work on a broken fork though. I'd have to be a preemptive move.

Anyone know a source for replacement forks?
This is a part I want to have on hand AND have it strengthened before installation.

The problem with an metal when you heat it you are going to soften the metal, to add strength to this part you are going to have to utilize a driving arc which will allow the stick to dig into the fork, once you are completed in adding the two welds the fork will be excessively hot. At this point you would need a secondary compound to cool the fork fast enough to reforge the fork, water would not add sufficient quenching to re-forge the material.

[HAWAIIZR-1]

Hello Jim/Yun,

What are your folks thought on the condition of the hydraulic clutch system being the most important factor? I don't know the details before the failure, but was it hard to engage at all or just felt normal? The reason I as is when my slave cylinder was failing due to defect of that reverse seal problem it worked normal at first then later got hard to depress and then nothing at all. I remember when Rich (no Screm, the other one) had a problem and bent fork it was difficult to depress and continued pressure ended up bending the fork, but not breaking it like this. So if there were not issues with the clutch system or the pressure plate then I agree too that just a defect in the part that eventually gave way.

[HAWAIIZR-1]

Okay, now I see Yun's original post of the problem and it appears no issue with the clutch system at all to contribute to the failure. Wow, I wonder what Bill B thinks of this issue? I did buy a spare fork from Jim Jandik earlier this year and I guess it is good to have one on the shelf just in case. Thanks for sharing this.

[scottfab]

Originally Posted by cvette98pacecar

http://www.powertorquesystems.com/Co...CorvetteCF.htm

[HAWAIIZR-1]

Originally Posted by scottfab

Scott, you're right on about Jim and he is first class when it comes to service and products.

[secondchance]

Originally Posted by HAWAIIZR-1

Okay, now I see Yun's original post of the problem and it appears no issue with the clutch system at all to contribute to the failure. Wow, I wonder what Bill B thinks of this issue? I did buy a spare fork from Jim Jandik earlier this year and I guess it is good to have one on the shelf just in case. Thanks for sharing this.

Hi Craig,

Hope all is well. As you noticed no issue whatsoever before the failure. I was lucky that it happened just as I was parking.
I agree that if my slave was failing and I kept putting excessive force the fork would have bent (warping of side flanges). Fact that it ripped makes me suspect defect around the rivet hole.

[HAWAIIZR-1]

Originally Posted by secondchance

Hi Craig,

Hope all is well. As you noticed no issue whatsoever before the failure. I was lucky that it happened just as I was parking.
I agree that if my slave was failing and I kept putting excessive force the fork would have bent (warping of side flanges). Fact that it ripped makes me suspect defect around the rivet hole.

Hey Yun,
All is well, thanks and hoping the same with you and family. I have been buried with work/school and inactive lately. Yes, timing was good for failure as a positive point like when mine (clutch slave) failed and I was at the traffic signal by my home; had to grind a few gears in the process. That rivet area does seem like it could be a weak point and defect as you stated. These forks seems to be a pretty stout item and I wonder where originally made and what quality of metal used? I guess the stuff from Jim Jandik is the best we can get being OEM stuff. Take care and thanks again for sharing.