Mr D.

I test fitted another new clutch disc to this transmission today and got the same results.

Here's the strange part, this transmission was installed in my last 65 project car that I drove home in 2005 and the car shifted just fine. For what it's worth this M20 transmission came out of a 1970 Corvette (CTO 40113).

I pulled it in 2007 and it's been in a box ever since, I threw away the clutch that came out of that car so I can't compare that to anything.

Well crap, damn whatever. I guess I'm looking at having this transmission rebuilt and a new input cluster gear installed.

DansYellow66

That's a shame. Can you see any sign of a twist looking at the shaft from the end? Unless there is a burr or something on one of the splines I can't think of another explanation for the disc not sliding freely.

A twisted input does make sense (at least to me) from what you are describing. It would start to twist right behind where the disc normally rests when the clutch is engaged (clamped to the flywheel) when power is being applied. So when the clutch is disengaged and the disc should kick back slightly from the flywheel, it can't because of the spline twist. A new or different clutch disc may have a slightly thicker hub that rests further back and holds the disc against the flywheel when the clutch is disengaged and create the symptoms that you described.

Mr D.

So while looking for my stash of transmission parts today I found the clutch set that came off this transmission in 2007.

The clutch cover is a Borg and Beck and the disc has no name or markings other than Made in USA. It's painted purple so I'm assuming its a Zoom part. As you can see in the picture it fits just fine and it a little looser than the LUK disc. It's pretty worn so I won't be able to use it.

This is all very strange and makes no sense, the disc I tried today at AutoZone was a Brut Power brand.

So I'm thinking now the input shaft is OK and I have a fit problem with aftermarket clutch products. I'm now leaning towards buying quality clutch set (McLoed or Centerforce) and see what this gets me.

Just weird.............

DansYellow66

Yes - pretty weird. I guess you could try to file out the spline grooves in the new disc to open them up slightly - but I suspect after all of this effort you are about ready to just find another disc that fits and get it back together.

66jack

If you cannot get it to fit with the new stuff...The next step is to put in an A U T O M A T I C....

Westlotorn

National Makes their 614018, I do not know if Timken makes the one they sell or buy it out.
The 614018 is a self aligning bearing and gives you a little extra ability to run a long life even if your clutch mechanism is off a little.

Since your older clutch works and slides freely on your input shaft I would take a file to the new clutch and repair the fit. Why toss a good part.
You might have it working with only few passes with the file. You can probably see the contact marks on your clutch that stopped the clutch travel.

Mr D.

At the advice of Westlotorn and Dan (Thank You) I did just that and the LUK disc now slides freely on the input shaft.

I used a file and homemade hone (emery cloth wrap around a bolt) and after several filings and test fits I could see I was gaining ground. Took about a hour of filing and test fitting.

Time to put this car back together.

Mr D.

You a very funny man.

I would need a dress to go with that transmission.

DansYellow66

We'll keep our fingers crossed. I'm not sure I remember a problem exactly like this coming up before so you may have hit on something truly odd with this.

Mr D.

Update:

Got the car back together today and the clutch works as advertised

However, after jacking the engine up and down my "Non Corvette" radiator fan rubs the fan shroud. It was a tight fit to begin with but it did have clearance. Oh well I guess this car was going to get money out of my pocket one way or the other. Off to LICS to buy more parts.

Want to thank everyone for all the input and interest in this clutch problem.

66jack

Glad you got it back on the road...

Westlotorn

Try loosening the tranny mount bolts and slipping it side to side to find your fan clearance. A small adjustment at the tranny is a big adjustment at the fan.
Glad the clutch is working well. Was the spline issue the major problem or did you trace it to something else?

DansYellow66

Good to hear - mystery solved. I second Westlotorn's advice on wiggling the transmission around a little to shift the fan away from the shroud. Might even loosen the motor mount bolts and see if the engine is sitting level from side to side or needs to be shifted a little.

Rustman

Been following and great you got it working.

Mr D.

I will give the tranny & engine mount bolts a shot to gain some fan clearance.

The clutch problem was the disk, I had to file fit the disc to the input shaft.