What Bent My Clutch Fork?

[Fishcop]

I've just begun stripping down my 81SC (915/62) box for a rebuild - straight away I noticed my clutch fork is bent and has been rubbing...





I'm guessing I had the clutch cable too tight and pulling the fork up against the bell housing webs? Any thoughts (the clutch was operating fine - though probably just a matter of time).

[moneymanager]

Hard to tell from pics but almost the only thing you can do to these, assuming they're in the correct operating position, is have the cable too tight. Next time make sure there is at least a tiny bit of slack. But some of this is just normal wear, if the fork has been in there for 100k miles or so.

[sc_rufctr]

I was thinking something this and this could have happened over a long period of time.

Every time you depress the clutch pedal you're putting a lot strain on that fork and eventually it will begin to fail. It's just an industrial reality.

For some reason the top didn't stay aligned with the bottom. Maybe there's less iron in the top finger of the fork... If you think about it all that would happen is that the release bearing was pulled away from the flywheel cocked backwards a bit at the top rather than straight. The release splines of the pressure plate would absorb this difference as you operated the clutch with the engine running.

I would expect that as our cars get older we'll see more and more of these sorts of failures.

As an example my Omega spring was cracked but to look at it you'd never would have known. I only found the crack after I removed it from the release arm so that I could change the needle bearings... Once I got it off it fell apart on my work bench. At that time I was going through the property settlement for my divorce which made me laugh at the irony... (Omega being the end..lol)

Hope it works out OK...

[Fast Corners]

It took me a minute to get my bearings on the issue since the 1st pic is upside down. I guess that would be normal for you Austrailians.

It's hard to see by the pic but it looks like the top part of the fork was not engaged. There should be wear on both arms of the fork. Were both arms in the groove of the throw out bearing? If only the bottom arm was in the TO bearing that would put a lot of stress on the single arm and could have bent it. Once bent, the TO bearing may have been binding and could have continued spinning during dis-engagement thereby creating the excessive wear. Just my thoughts.

[Fishcop]

FC - yes we are an upside-down lot The bell housing is just sitting on the floor so I didn't think to get orientated.

Peter, they reckon we should change the fork with the clutch just to be sure - I've got a spare, so I'll throw it in.

I'm quite sure both forks were in the groove (at least when I last buttoned it up). What makes me think the cable was too tight is that the fork "off-set" matches perfectly with the back profile of the bell housing... I guess I'll just have to take more care when it goes back in.

Cheers

[sc_rufctr]

John

Triple check your Omega spring on your release arm. It's easy to do. Take it off the arm and hang it with a piece of string. Tap it lightly with a hammer. It should ring like a bell. If it's cracked it won't ring clear... more a dirty ring if you know what I mean.... Sorry but that's the best way to describe it.

I paid about $70 for a new one from a Porsche dealership.

The needle bearings for the Omega spring shaft that goes into the release arm are also available. About $12 each... (x2 stacked on top of each other)

After I changed my Omega spring it was very easy to adjust the small gap needed on the release arm. A small detail but the clutch action felt perfect afterwards.

I can post the diagram from the Haynes manual if needed. Just ask.

[Rumble-Bee]

Check your floor board and clutch pedal stop adjustment under the dash. I'm not sure how your car is setup but I have broken clutch fork ball pins twice on 2 different early Porsches because the floor board was falling apart. There is an adjustable clutch pedal stop on the floor board of my 70 911T. If it's not doing it's job it is easy to snap clutch parts because your foot is pushing beyond the designed travel limit of the clutch.

[Fishcop]

GDuchanin - I think you're on the money, I don't have a floor board there at all...

[Wayne 962]

Interesting diagnosis - we sell the forks and floorboards and springs to fix this. I probably would not have thought of the floorboard as the immediate culprit...

-Wayne

[Fishcop]

Hi Wayne, I don't think you do RHD boards do you?

A few people I've talked to think that it's likely to have been my hoofs pushing too hard on the clutch pedal without a stop...