68 C20 new clutch won't disengage

[cjoenny89]

Throw out bearing was installed correctly. I know that for a fact.
The clutch disc is tight and rubs a little on the bolt tabs but I didn't that that was enough to stop the clutch from working.

[cjoenny89]

I guess I am at the point of buying a different brand of clutch? Just not sure what to do next other then a different clutch

[geezer#99]

Did you test fit the disc on the flywheel to see if it sits flat on it?

[cjoenny89]

Yes it sits flat and will spin with no hang ups.

[geezer#99]

And if it does the same with the other side on the pressure plate then bolt it togethor.

Did you leave your fork inside the bellhousing hooked onto the ball?

[cjoenny89]

It only spins with the flat side down and if you flip it around it won't spin or sit flat.
Yes I left the fork in the bell housing should I have taken it out?

[body bolt]

Perhaps you got the wrong clutch or ???. The cover and disc don't seem to match.

[geezer#99]

You don’t need to flip it around.
It fits the flywheel. Done deal.
Then I assume it fits to the pressure plate. I was just making sure of that.
Your pics show raised fingers with a short throw out bearing. That’s a match.
As long as your fork is in right and swivels nicely, all is good.
Put it back togethor and run it.

[LockDoc]

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Clutch disk looks too big to me. The pressure plate is pinching it when it is bolted up. I would try a smaller disk if it was me.

LockDoc

[Steeveedee]

Originally Posted by LockDoc

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Clutch disk looks too big to me. The pressure plate is pinching it when it is bolted up. I would try a smaller disk if it was me.

LockDoc

Yup, that's why there are chunks munched on the perimeter of the disc.

[kwmech]

Uhhhh, yeah.....see posts 22 and 23

[cjoenny89]

If I measure the clutch disc and pressure plate surface it measures 11-7/8" or real close to that. The truck calls for a 12" clutch set up. When you bolt up the pressure plate should it not sinch down on the clutch disc?
What do you mean it is pinching the clutch disc when bolted down causing the problem?

[kwmech]

Originally Posted by cjoenny89

What do you mean it is pinching the clutch disc when bolted down causing the problem?

Look at your own pictures. The disc is clearly being pinched somewhere on the edge of the plate causing damage, find out where. Give us a picture of the other side of the disc and a full picture of the disc centered on the plate close up

[Steeveedee]

What is the outside diameter of the pressure plate disc? Maybe the clutch disc got damaged some other way.

[cjoenny89]

I am thinking that I got of center just a little and it got clamped down near one of the bolt hole tabs.

[cjoenny89]

Here is one with the clutch disc centered on the pressure plate

[HalfBrit]

I realize this has been mentioned already, but, the clutch and pressure plate friction surfaces should be the same size. The clutch friction surface does seem to be crowding the pressure plate flanges. Details like this can certainly cause frustration. Been there myself, more times than I care to mention.

[body bolt]

It's not just the diameter that matters. The cover is assembled to match a particular disc including the thickness. You had a finger cover and now you have a diaphragm cover. Why didn't they give you a finger cover?

[cjoenny89]

I didn't know I had a finger clutch until I tore it apart. Once I tore it apart every parts store I looked up the pictures shows the diaphragm clutch and seems no one sells the finger clutch.

[geezer#99]

Summit has them.
The three finger is actually called a borg and beck style.


https://www.summitracing.com/parts/zzz-mu1862-1

[Steeveedee]

Either should work. But I think that there is a difference in the throw out bearing between the two. It's been a dog's age since I've replaced a clutch. If the diaphragm clutch takes a taller throw out bearing, that would explain your predicament. How much free pedal do you have on the clutch pedal?

[cjoenny89]

I bought it as one clutch kit. The free play was how I left it from the original truck.
I then lengthened the adjustment rod and had no free play throughout bearing was tight to the pressure plate still couldn't put it in gear. So I then took it all back apart.
Here is the 2 throughout beatings. New on left old on right.

[54blackhornet]

The last photo clearly shows a difference in overall height.

[kwmech]

The new diaphragm clutches have the same amount of clamping pressure as the old 3 finger plates for street application. Also the diaphragms are easier on the linkage points and the knees. All in all measure the metal plate and that will give you your clutch diameter. Last 12'' clutch I put in was at least 10-11 years ago in my tow truck with a 454. I got the kit from GM and it was a diaphragm. I removed a 3 finger, everything went in smooth as silk and the clutch was awesome to use after that.

[cjoenny89]

Originally Posted by 54blackhornet

The last photo clearly shows a difference in overall height.

The throwout bearing matting service to pressure plate to clutch fork is the same height. The extra length is out the back towards the transmission. That extra length shouldn't hurt anything. Look at the picture with the bearing surface down on the table it shows the fork location in the same spot. Unless I am missing something the extra length in the back shouldn't matter.