Old release fork broke after new clutch installed?

[wesleyc]

Is this just bad karma ? Or has it happened to anyone else when keeping your old release fork it breaks the first clutch pedal press you give it after new clutch/flywheel !?! Another question. If only putting in new release fork. Would it be easier to just drop the tranny instead ? I'm Working alone so I don't want to get myself in to deep on a one person job. Which I pretty much am already. Thanks all

[nickd]

Sounds pretty odd. Are you sure that it all went together correctly? Did the pedal feel like it was binding before it broke? Correct clutch/pressure plate/flywheel combo? New throw out bearing? New fork bearings? New TO bearing shaft? Correct grease on the guide tube? Clutch fork shaft is good and straight?

Not sure that I've heard of one braking from fatigue. A bent fork shaft isn't unheard of, possibly caused things to bind.

I would pull the motor/trans together. Quite a pain to separate them, let alone put them back together, while leaving the engine in place. Much easier to remove the assembly.

[wesleyc]

Thanks for input. I'm going to start dropping it all tomorrow. It's gotta be something I did? Yes I put in new everything except the fork ?

[Spenny_b]

Yeah, I have heard of one other fork breaking - have a read through Rob's 964 resto project here, towards the tail-end of the thread there's discussion about the clutch release arm assy, with one guy commenting he had the finger of one snap.

There've been a number of fork revisions over the years, it now has a 997.xxx p/n. I bought a new one a few weeks ago (along with everything else like shaft, seals, bolts, brackets) as part of my Sachs Racing / 997 GT2RS clutch pack going onto a 964RS F/W - the contact surfaces of the new fork are about 2x the size of the original part I had. The bushes have also changed from sacrificial metal to plastic, although my old one must've been an intermediate item; short contact faces + plastic bushes.

[bazar01]

If you need a workshop manual, let me know. That will help a lot.

Make sure the fork is taped to the pressure plate when you put it back together.
Here is a diagram. Hope you get it back on the road again.

I have reused my fork and it has been 50k miles now. I just upgraded to the bronze bushings to replace the needle bearings.

[wesleyc]

Thanks guy's. I'm gonna muster up the some enthusiasm to drop everything again tomorrow. I don't have a clue what I did wrong until I pul it apart ? I'm Sure it was some brain fart I had ? All I know is if I get this thing back together and mess something else up I'll be found on the garage floor in the fetal position sobbing!! Or at least extremely upset. Thanks for your support. I really appreciate it.

[wesleyc]

Bazar01 I don't have anything but the Bentley manual. If you've got better I'd soo appreciate it !! Thank you !

[aabarth]

I would think that going this deep into the motor/trans/clutch would require the factory manual.

Not the car I would choose to learn about cars on !

[wesleyc]

Yes. Now that I've tried this repair with the Bentley I agree!

[iamtheari]

Not to thread jack, but does anyone know where in the manual the torque specification for the engine-to-transmission flange fasteners can be found? That one seems to be missing from the engine removal/installation portion of the workshop manual and I can't find it in the transmission section, either.

[wesleyc]

17lbs.

[Matt Monson]

Hopefully the case itself didn't break. Unfortunately as these cars age it is becoming fairly common. California Motorsports can repair it if the case is broken.

[Bill Verburg]

Was it the fork that broke or the bushes?

We are seeing the bushes fail regularly

[wesleyc]

Bad news!! I dropped the engine where I could see it good and it's the transmission casting that holds the shaft and fork. What do I do ? I don't think a casted piece can be welded? My first clutch change is a disaster so far ! Amy advice? Thank you.

[aabarth]

Bummer, but these can be repaired.

[sand_man]

To the OP, I'm sorry for your troubles!!! I absolutely HATE having to "go back in", after I've gone to all the trouble to get it back in the car and everything buttoned up!!!!! UGH!!!

Soon I'll be doing a mid-weight flywheel and associated clutch parts in my 993 C2 and I am curious what model this is; 964 or 993? And if this failure is prevalent in one model over another (between 964 and 993)? And finally, is there anything that can be done to mitigate this breakage? My car is a daily driver, so I plan my repairs carefully over the weekend. If there's something I can do to avoid doing it again, I want it.

[bazar01]

The first question to ask is "How was the pedal effort before the clutch replacement?"

If the pedal effort was too heavy, there was a possibility the needle bearings were seized on the fork shaft that put a lot of concentrated load on the casting ears that hold the cross shaft and caused stress cracking.

Preventive actions include.
1. Timely clutch job. Do not wait too long for a clutch job esp if the pedal effort is getting heavy.
2. I would always go with stock components so as not to put more than designed loading on the cross shaft ears especially the pressure plates.

[wesleyc]

Sandman mine is a 95 993. Mine WAS my daily driver also... Bazar01 my clutching wasn't heavy and I went back with stock components. The little plastic cap that goes on the end of the fork shaft couldn't be found. But when I separated the trans from engine the bearing was in tight ?

[wesleyc]

I'm guessing I need to find a shop with a good welder. I still am wondering what went wrong? If I assembled clutch disc to pressure plate incorrect ? I followed the tob install correct to directions? Or just timely metal fatigue? I'll scratch my head a bit more about this.

[bazar01]

Originally Posted by wesleyc

Sandman mine is a 95 993. Mine WAS my daily driver also... Bazar01 my clutching wasn't heavy and I went back with stock components. The little plastic cap that goes on the end of the fork shaft couldn't be found. But when I separated the trans from engine the bearing was in tight ?

When I did my clutch at 100k miles, the fork cross shaft came out really easy with a slide hammer and did not show any needle marks on the shaft bearing journals. But I replaced it with a new one and updated to bronze bushings. If I think about it, I should have gone back to needle bearings because I can feel now the bronze bushings are binding a little. The plain bronze bushings have no grooves for the grease lube and it seems like it is starting to bind now due to absence of lubrication.
I may need to drop it again in the next 5 or 10k miles and go back to needle bearings.