mpopp2002

Hoping for some help with a clattering noise coming from the clutch of my 1970 L46 with Muncie M20... I had the car out yesterday and was doing some "spirited" driving and started to hear a slight rattling noise. I pulled into the driveway and could hear the rattle more clearly. Here is what I noticed:
- With the clutch engaged, the rattle noise was very quite... Almost unpreceptable inside the car
- When I let the clutch out, the rattle was very pronounced.
- if I push the clutch in a half inch, the rattle sound is almost gone again

Engine running smooth at idle and RPMs
Car shifts perfectly

Any ideas to get me started?

keithinspace

I'll throw a thought out there:

Pilot bushing issue?

If I understand correctly:
--Clutch pushed all the way in (disengaged)...nothing. No rattle.
--Clutch pedal completely released (drivetrain engaged)...shaking.
--Clutch pedal partially depressed...better, but still there.

If the pilot bushing is worn to the point of not properly locating the input shaft, is there a chance the clutch plate itself is not being "squeezed" in the center of the flywheel and the whole assembly being out of balance while rotating?

I'm a big dummy, so please someone offer a better idea to help this fine man.

claysmoker

Might be the spring clip on the throwout arm is loose or one side of the clip is broken off.

marshal135

I was thinking the fork spring fell off.
The fork will rattle w/o it.
Marshal

toobroketoretire

It sounds to me like the fork's pivot ball has loosened over time and screwed itself foreword; the fork now nipping the rear of the spinning pressure plate. To check it put it up onto safety stands and crawl under it. You'll be able to see the head of the pivot ball with it's 3/8" Allen socket hole right below the upper left 1/2" NC transmission/bellhousing bolt. To put the ball back where it should be turn it counterclockwise with a 3/8" Allen wrench or Allen socket until its TIGHT; the head being almost flush with the rear surface of the bell housing.

mpopp2002

Thanks for the advice gang. I am new to the C3 having just sold my C5 a few months back. I will check this out on Friday when in get back in town!

claysmoker

Really??? It's gonna be damned tough to get to the pivot ball without removing the transmission(or at least pulling it back a couple of inches), plus the fact that the pivot ball screws in from the rear of the bell housing and can only move aft if it loosens. How is it going to contact the pressure plate if it can only move away from it?

Please tell me how this works? Is this some new magic you've invented?

toobroketoretire

You are just plain wrong! The pivot ball screws in from the inside out (toward the transmission). The Allen head is fully visible between the left side transmission ears and it can be easily accessed with either an Allen wrench or Allen socket.

Do you see the big round thingy with the 6-point Allen hole in it? That is the thing you say isn't able to be accessed.

claysmoker

Here you go.

toobroketoretire

What am I looking at? The pivot ball gets screwed in by hand FROM THE INSIDE OUT until it's flange bottoms against the inner machined face of the bell housing. Then an Allen wrench or socket is used to tighten it. Its always best to coat the threads with blue LocTite to ensure it never unscrews FOREWORD against the pressure plate.

If you are using a later transmission other that an ordinary 4-speed of the period it would be possible to cover the Allen hole.

By shortening an Allen wrench you can easily turn the pivot ball counterclockwise until its good and tight.

claysmoker

The same thing as you posted. The standard pivot ball screws in from the tranny side of the housing. There is a flange on the aft side that prevents it from going further into the bell housing. I'd suggest you go get a really big hex key with a long arm on it and try to turn that pivot ball clockwise.

You might be thinking of an adjustable pivot ball. They screw in from the inside and have a lock nut holding them against the flanged nut that comes in from the tranny side.

toobroketoretire

Having the pivot ball loosen and screw it's way foreword against the pressure plate was common problem I ran into when I used to work on G.M. muscle cars at my home. Had the factory installed the pivot ***** with a thread locking compound on the threads it wouldn't have happened. Before LocTite was invented we used to use ordinary enamel paint which accomplished the same thing but took a lot longer to cure.

claysmoker

FYI Loctite was invented in 1953. Early muscle cars?

claysmoker

Here's what a stock clutch fork pivot ball looks like. I defy you to screw one in from the inside of the bellhousing.

http://www.summitracing.com/nv/parts...0556/overview/

Another one for you:

http://www.summitracing.com/nv/parts...6/applications

toobroketoretire

Uh uh, the pivot ***** screw in from the clutch side of the bell housing toward the transmission; not from the transmission side in. Take a look at a pivot ball and see how its made. The OEM pivot ***** don't come with lock nuts; just a flange that bottoms out against the inside of the bell housing.

claysmoker

Go look at the adjustable type. Then you would be correct. The one in your photo screws in from the rear, as does the one in my photo.

Here's an adjustable:
http://www.summitracing.com/nv/parts/lak-15501

There are many brands, and they all work the same way.

toobroketoretire

I just checked out Summit Racing and see they sell several different styles of Chevrolet pivot *****. The OEM ball in my '68 screwed in from the inside out but the ones I saw in Summit Racing screwed in from the outside in. My OEM pivot ball was screwed in so far my fork was rubbing against the pressure plate. The bell housing had a 4" crack in it that ran thru the pivot ball threads so I took it off and had it welded. That's when I discovered it was screwed in from the inside out just like the several others I had come across back in the 1970's. So it appears they're not all the same.

croaker

OP I agree with the theory of your clutch fork being the issue. If it is the clip you can get just the clip and a big rivet from Willcox for less then 20 bucks instead of whole fork for a crispy Hundred. My clip broke last year

MotorHead

I always use the adjustable Lakewood clutch pivot *****. Once I get the correct length I tack weld the holdown nut. I am not aware of any adjustable type be it OEM of aftermarket where you can adjust the length outside the bellhousing.

To get the correct length Lakewood has a measurement paper and is usually spot on. If not you have to pull the tranny and bellhousing to make adjustments (big hassle). The OEM non adjustables are the short version and long version both of which may or may not work depending on the type and manufacturer of the clutch. If I am wrong here and there is an easier way I would like know