Clutch chatter...

My CAV (mono #8) has major amounts of clutch chatter. The engine is a crate 302 (about 325hp) with the Kennedy adapter plate and Audi 016 (AAZ). I believe the clutch is a "five button" but I'm not positive.

When accelerating slowly or moderately from a complete stop there is a fair amount of juttering from the driveline. I can see the engine shaking (the Holley carb through the rear view mirror is the indicator), specifically, some slight rocking motion fore/aft. I do not know the condition of the CV axles. The engine and transaxle mounts look to be in fine shape and are made of black rubber.

Any recommendations to rectify? Thanks in advance.

Can you clarify this a bit Cliff. Does the 'juttering' only take place as the clutch is being engaged, or continue on as you accelerate. If you slow down then accelerate without using the clutch does the problem still exist?

Jac Mac

shudder

Cliff

I have a customer who put a button clutch in his 40 & it does exactly the same.
I have to give it a few more revs to stop it doing it.
The whole car shakes.

I have put a few of these in turbo cars and they generally feel ok.
I have wondered as the eng and trans mounts are much stiffer on these cars if it is having an effect.

Is it a solid centre or a sprung centre in the plate as this can help?

Jim

We had this problem in trucks using ceramic button clutches. It takes a long time to wear in and it will go away in time. Some drivers could actually break diffs and driveshaft when heavily loaded on take offs because of the chatter/shutter.

I just install a relined clutch disc with Kevlar and I am getting the same thing. Very annoying but I hope it will go away in time.

Jim

CliffBeer,
In case it helps, this was an issue with Subaru Impreza Turbo's. Mine has now done 109,000 miles and still does it. Some people had clutches replaced (same or different types I dont know) under warranty, but in many cases it didn't help much. That is because the problem is a combination of factors, clutch judder, torsional drivetrain response, and suspension dynamics, not just the clutch.
On my Subaru, I can drive around the problem by taking off gently, or briskly but not in between. Another way of putting it, if we have a scale of take off between 1 (very gentle low revs) and 5(dropthe clutch high revs) I use 1, or 3 to 5, but not 2.
It happens especially when the car is cold if I forget to do that, and when it does I have to come off the throttle or it wont stop.
Without changing the clutch, other things that might affect it are suspension and engine mount rubber hardness, and spring rates.

Dave

Clutch type

If you are using a three, four, five, six or whatever puck type clutch you'll usually get some grabbing on engagement from a take off. At least, that is the experience we've had with them in the race cars. Every car we put a clutch type puck has this grabbiness, while the original clutch did not have this behavior. Particularily shows up on Miatas, which are very light at around 2100lbs in race trim.

However, it is simply grabby upon engagement and after that is fine. It doesn't continue once the clutch is fully engaged.

Ron

Cliff
I have seen the same with the button type clutches, and some other types of conventional clutches if the flywheel surface has hard spots...usually caused by overheating, which would mean a slipping clutch. It doesen't sound like that is your problem. Another problem we have found is the linkage..if the slave cylinder is attached to the engine or bellhousing there is usually no problem, but I saw a setup where the slave was on a bracket on the chassis, and when clutch engagement was required the motor would flex on the mounts causing the distance between the slave and fork to shorten, de-coupling the clutch ...this made the motor relax, which brought the clutch back together again...the result was a serious chatter. I would check also to be sure that your flywheel surface is true...most clutches only have about .060" clearance at disengagement, and little imperfections can have a large effect, I hope some of this may help.
Cheers
Phil

Thank you all here - very helpful information.

To answer a couple of the questions:

1. The jutter is only on take up. Once fully engaged and under way there's no jutter. The 1st to 2nd gear change is not a problem, it's really just moving away from a dead stop that produces some shaking.

2. I don't know the condition of the flywheel. I did notice that two of the six Kennedy adapter plate bolts were missing when I acquired the car, specifically, the lower two bolts of the six. This allowed the engine to flex relative to the transaxle (most obviously while in reverse). I suspect the flywheel may need resurfacing to get it true again.

So I guess one question I have is, is there a more moderate clutch package that can be used with the SBF/Kennedy adapter/Audi 016? Something with a smoother take up?

Thanks!

Sorry for delay in replying as I saw post yesterday but no time to post till now.

This judder you speak is very very common on paddle/button type friction plates. A lot of GTDs have it including mine. There are two ways of dealing with it, none of which involve any mechanical work.

On pull away you are used to a typical pull away amount of RPM from your old clutch system. This will need to be changed. Either bring the clutch in without any additional RPM or increase the RPM used to about 500 rpm above what you used to do. Both of these driving technique changes will reduce if not remove the judder completely. You have a competition style friction plate now. It is not for pussy footing about so abusing the clutch is what it likes. Drive with committment!

I have tried these friction plates both with and without springs in them. It makes zero difference to the judder.

Hope this helps.

Any of the bronze/ceramic friction disc's that I'm familiar with, normally require that the flywheel and pressure plate friction surfaces have a very smooth finish. A typical rough blanchard ground finish used for organic friction disc's is not suitable, and will produce abrupt coupling that leads to chatter. This has been my experience. One race clutch manufacturer I dealt with opinied that a spring center sometimes makes chatter worse when used with an aggressive friction material such as bronze/ceramic.

Andys

andys said:

Any of the bronze/ceramic friction disc's that I'm familiar with, normally require that the flywheel and pressure plate friction surfaces have a very smooth finish. A typical rough blanchard ground finish used for organic friction disc's is not suitable, and will produce abrupt coupling that leads to chatter. This has been my experience. One race clutch manufacturer I dealt with opinied that a spring center sometimes makes chatter worse when used with an aggressive friction material such as bronze/ceramic.

Andys

Click to expand...

My TR7V8 has a twin plate sintered bronze setup and is very progressive. The lack of expected judder and snatch I attribute (rightly or wrongly) to the use of a concentric hydraulic TOB.

Cheers