Bent Clutch Fork
 

My clutch failed to disengage over the weekend and I had to tow the vehicle home. After tearing everything down, I discovered that my clutch fork was bent where it holds the throw out bearing. I have no idea how this could have happened. The pressure plate diaphragm looks fine.

Photos of clutch fork below.

Any ideas on what could cause this?

Driving a stick with sandals

Who did you buy the clutch fork from?

Tom V.

Is it a repop?

Summit:

Goodmark GMK4330951641

https://www.summitracing.com/parts/GMK-4330-951-641

I will remove the pressure plate, clutch, and flywheel tonight to ensure it is all OK.

Thursday afternoon I'm visiting a clutch specialist to look over everything and get a new fork and throw out bearing. Hayes flywheel, Center-Force clutch, PP, and TO bearing. DF735552

https://www.centerforce.com/product/...269751-c545805

Question, Is there anything special about the Pontiac fork, aside from the groove for the 64-65 return spring? Specifically about the geometry?

I just went through the same thing with the Goodmark fork and then one from Inline Tube in my 1967 GTO with a Centerforce 2 clutch and a Autogear M22W. Where the throw out bearing goes the OEM fork is rounded and both aftermarket forks it was straight in that area. I ended up finding a OE fork part number 9787069 and put in a (Mcleod adjustable pivot ball 16908 and the part that goes in the bellhousing had to have the thread cleaned up to make it fit) and set per the Centerforce instructions and so far so good.

That's interesting. I was assuming that I put the throw out bearing on askew, and that caused the failure.

You are right, it is straight where the throw out bearing rides on the fork. I will run that by the clutch pro when I see him. He said on the phone that they stock clutch forks for old GM, but they are not Pontiac specific and he was unaware of the Goodmark repop clutch fork, and said it looked odd to him. He asked that I bring it in Thursday.

Do you have any idea where I can get an OE one for '65?

I just did a 4 speed conversion for a 70' GTO and used pedals and linkage parts from our host. After finishing, I couldn't get the clutch play adjusted right for nothing. If I got a little play with the peddle up, it was out of adjustment at the bottom, and visa versa. I finally pulled the transmission back out and found the clutch fork was the incorrect length from the clutch pushrod to the pivot point where the clutch ball sits. That's comparing it to several original clutch forks I had laying around. Also, the clutch Z-bar had a lot of slop at it's pivot points and therefore was flexing. I put stock components back in, and reinstalled the transmission AGAIN, and it was good to go.

Thank you for that info. I have a line on a OEM clutch fork. I'm going to take all my components to a special clutch shop tomorrow and talk it through with them. I spoke to Russ at 4-speed Conversions at length this morning, and he doesn't know what could have caused the fork to bend as it did. I told him that I assumed I installed the TO bearing askew, but he says I would have known immediately.

Here's a pick of my front bearing retainer. Note that the damage / wear is not completely around the shaft. I ordered a new one tonight. I am unsure if I could have polished this and called it a day as opposed to buying a new one.

Yes, it could. But, better safe than sorry, I will replace. The TO bearing and snout were bone dry. Maybe I didn't lube the inside of the TO bearing and that caused binding and it seized?

Looks to me like the one sprung finger was placed on the wrong side of the throw out bearing during install, and it loaded the bearing cocked on the trans bearing retainer, and/or got hung on some pressure plate fingers. (see attached pic)

I bet it happened during install of trans, when trying to get the input shaft into the disc. Maybe when 'giggling' it, or using the bolts to pull the trans up to the bell. (which is a no-no)

I would make sure none of the pressure plate fingers are bent, and if not, you got lucky. Should be able to replace the fork and bearing, and proceed.

EDIT: NO lube should be used on the throw out bearing or on the bearing retainer.


.

That was my initial thought as well. During tranny install, my friend was helping and knocked the TO bearing loose and put it back on. I didn't double check it that he put it on correct and he isn't knowledgable about such things.

However, others have told me that I would have immediately known when I tried to drive the car, as I would have had major clutch issues.

I've put about 500 miles on it.

It would make some additional noise, but it could still operate somewhat normally. If you have a loud exhaust, you may not hear it.

The throw out wouldn't sit squarely on the plate fingers, and the one side could drop below the fingers even. That is what could have actually bent the one side of the fork, fingers holding the bearing towards the plate, while the other fingers pushed back into the released position.

But of course, it's only speculation.

Since it's apart, inspect the PP closely for damage. If it loaded the bearing enough to bend the fork, I would guess there is PP damage too.

Is there an inspection hole on the bottom of the bell, or is it a blow-proof? If a blow-proof, I would be looking for the piece that broke off the fork. Hopefully it's not in the PP somewhere, or worse, between the disc and flywheel/plate.

If there's any damage to the PP, don't screw around, replace it all. If the flywheel has a gouge, have it turned.

.

Rebuild the Z-bar, all the parts are available.

https://www.ebay.com/itm/11487203600...SABEgLomPD_BwE

If you want, you can upgrade the linkage too:

https://www.speeddirect.com/clutch-linkage

.

Everything is apart. Below is a picture of the pressure plate. No visible damage or wear. There was no debris anywhere. I am bringing all the parts to a clutch shop this afternoon and having them look at it and render an opinion.

HWYSTR455 - I called SpeedDirect about that linkage. they don't have a kit available for '65 GTO. The tech person was unsure if their 64'-67' Chevelle linkage would work. Did you purchase it and it works for you?

You have to measure, but pretty sure it works on any 64-67 GM A-body, they are basically all the same. I personally don't have direct experience with 64-67s.

If it's a length issue, all you have to do is cut the rod, and thread the clevis in. You could also buy a longer rod if need be, and/or bend it more.

.

Yeah, that doesn't appear to have any damage from what I see in that pic, but probably good you're going to have someone check it too. A couple sets of eyes on it helps.

The additional info on your friend knocking the bearing loose during install makes me think that was to 'cause'.

And, just to throw it out there, you could if you wanted to, change the location of the hole in the Z bar/bell crank to change the 'throw' distance.

For example, on my 'bird, I drilled another hole closer to the end of the Z bar 'tab', so it requires less pedal distance to equal the same 'throw'. That allowed me to put an adjustable stop in the pedal bumper, and adjust it closer to the floor, which made it more even with the brake pedal.

My adjustable stop was simply a grade 8 bolt with 2 nuts, and I used a vacuum cap on the end to absorb virbation.

.

There is an opening on the back side of the bearing retainer that lines up with an oil hole in the transmission case. If it is not installed the correct way, the oil hole is blocked.