Clutch Chatter & Flywheel run-out

[BRENT in 10-uh-C]

We are exploring a fairly rough clutch chattering situation on a vehicle that has been mechanically restored prior to this person owning the vehicle. Initially we removed the transmission thinking we would see a worn pilot or main drive gear end that engages into the pilot bearing. All of that appears to be new and not the culprit. The flywheel has been converted to the V-8 clutch style P/P and has a new pilot bearing. We just indicated the housing and it is between 0.004" - 0.005" with the majority of the run-out on the lower portion. Not sure how much the physical weight of the transmission would lessen that amount (-if any) when it is installed.


The flywheel face still has the grinder marks, and although they are a little rougher than what most would like by today's standards, it does appear the clutch is engaging uniformly for the most part and probably not the culprit. The flywheel face appears to have approximately 0.008"-0.009" of run-out in it and was indicated on the outermost portion of the flywheel face near the pressure plate holes. I suspect this was introduced when the flywheel was machined, HOWEVER I also do not know if this much run-out is really a problem either. I know there has been a number of something like 0.005" maximum runout for a flywheel offered numerous times here however if I recall correctly, that number is taken as a spec designed for the multiple-disc clutch and may or may not necessarily be applicable for the 6375B flywheel.


So where my question(s) would be is exactly how much flywheel face variance/runout is acceptable before it would actually give a problem? Why I am asking for opinions is kinda two-fold in that this flywheel has been balanced along with the P/P. If I were to set it up into the flywheel grinder to take off the 0.005" to true it up, then I potentially would need to rebalance the flywheel and P/P. Not a big deal if it were to cure the issue but it would be perceived as a wasted expense if not the culprit. Thoughts??
.
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[Patrick L.]

Hmmm, interesting. My thoughts are that there is too much runout in that wheel. I've always thought that about .002" was the accepted number. How much more than that would cause your problem, I guess I'm not too sure. But, I think your .008" is way too much. That said, taking off the few thousands to true it up, I wouldn't think it would need to be rebalanced. Personally I would try that. I understand your predicament, time is money and we know how much time it takes to pull these critters back apart. I'm sure we'll all be interested to hear about the outcome.

[BRENT in 10-uh-C]

Originally Posted by Patrick L.

Hmmm, interesting. My thoughts are that there is too much runout in that wheel. I've always thought that about .002" was the accepted number. How much more than that would cause your problem, I guess I'm not too sure. But, I think your .008" is way too much. That said, taking off the few thousands to true it up, I wouldn't think it would need to be rebalanced. Personally I would try that. I understand your predicament, time is money and we know how much time it takes to pull these critters back apart. I'm sure we'll all be interested to hear about the outcome.

Ok, some additional food for thought.....


If I take 0.002" off of the flywheel, how much do you think that removed material will weigh? Using a clock face for a visual reference for this illustration, theoretically if I take 0.002" off the flywheel face, then I will be taking approximately 0.001" off from the 4 o'clock to the 5 o'clock position along with 0.001" from the 7 o'clock to 8 o'clock position and approx. 0.002" from the 5 o'clock around to the 7 o'clock position, ...or about 120° of the flywheel. The remaining 240° of the flywheel perimeter is not to have any material removed. While I can probably calculate the weight of that material which would be removed, by guess I feel like it would be at least 10 grams, ...which in the world of balance should/would be noticeable on a flywheel.


Since you mentioned recalling the 0.002" runout number, I went to the source to find exactly what that number is. On page 218 of the Service Bulletins, it mentions a number of 0.005" as the maximum number for being eccentric and without wobble. It states to measure this at the hub and rear face of the large diameter. The issue with this number is we are speaking of a multiple disc flywheel that is only been machined in the clutch hub (...in the center). So if the "wobble" is to be measured on the multiple-disc hub, it is only ½ the distance to the outer perimeter of the flywheel. Therefore, if we use the 0.005" maximum of wobble on a multiple-disc flywheel, then on a regular Model-A flywheel that max number would likely double if the radius of the flywheel measurement were doubled too. With that mindset, then 0.010" would be the maximum number of run-out. Would it not??

[Jim Brierley]

Brent, I don't think that .008" would cause your chatter problem, nor removing it would be cause for re-balancing. I chased the same problem in my tudor. I replaced the float-o-motors with original mounts, helped a little but no cure. I later changed engines, with a fresh-ground flywheel and V8 PP, not enough improvement to speak of. The last change was to a diaphragm clutch, that helped immensely, for all practical purposes it cured it but occasionally (rarely) a bit of chatter could still be felt. I don't know why some A's chatter, but that's my story. BTW, changing to stock motor mounts did not affect the overall smoothness one iota!

[Patrick L.]

I don't remember ever seeing a spec for an 'A' flywheel. The number I posted is a generally accepted spec for most stuff. Some are spec'd much tighter, [I have read some specs in the past that were less than .001".] If I cut one or had one cut I'd expect it to be within that number.
I don't think the 10grams could be considered to be removed from one spot on the wheel, it would be spread out. I think I'd still run it without balancing, but as said, it would be just time for me to remove it again if I had to. I wouldn't be very happy about it, thats for sure.
If the other measurements seem good including the finger heights, crank end play and motor mounts etc then I'm at a loss. Maybe the disk or pressure plate has a problem.

[john in illinois]

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The foreign made new V8 clutch pressure plates have an extensive history of chatter on Ford Barn V8.

John

[john in illinois]

...

[BRENT in 10-uh-C]

Originally Posted by john in illinois

The foreign made new V8 clutch pressure plates have an extensive history of chatter on Ford Barn V8.

John

Interesting. Does anyone know why?

I have not experienced it with the flywheel conversions we have done. The only thing that I have heard is they possibly do not have enough clamping force on tall(er) geared vehicles.

[BRENT in 10-uh-C]

Thanks Jim. This engine has stock rear mounts. By diaphragm clutch, you are speaking of a diaphragm pressure plate and not the fingered Borg & Beck style P/P, -correct??


The reason why we have not suspected the flywheel per se' is sometimes even pressure plates will have their plate release/engage at a slight angle that would be at least 0.008-0.010 or more.


Here is some of the talk we have had in-house. Theoretically, the transmission main gear (input) shaft should be running very close in concentricity since the pilot bearing and shaft end are very tight in fit, ...and there is a new bearing in the transmission case holding that end where the disc cannot jump out of centerline when it is engaged. It also appears the clutch housing is piloting correctly on the front bearing retainer however maybe something is off there? We have discussed mounting the clutch housing onto the bed of the mill and indicating/sweeping the flange however my mill table is only 9", so I am not sure how accurate we can measure with the equipment I have. I do have access to a surface plate that maybe we can check it with.


One other theory we have discussed is that clutch discs have some spline to shaft clearance to allow the hub of the disc to float on the shaft during pressure plate disengagement. I do not have a print on the transmission shaft nor on the clutch to reference sizes, but is it possible that with a few thou. of clearance in the fit that the clutch disc (-which likely is never balanced) can move slightly out of centerline enough to create just a small amount of chatter?

[BILL WILLIAMSON]

Brent,
Use a smooth, idling, second gear take off, for a Month. This smoothed out Minervas' clutch perfectly.
Bill W.[/B][/B]

[roy green coupe]

Originally Posted by BILL WILLIAMSON

Brent,
Use a smooth, idling, second gear take off, for a Month. This smoothed out Minervas' clutch perfectly.
Bill W.[/B][/B]

I think Bill is on to something here. I have also had the experience of
a new disc and pressure plate needing some wear to work smoothly. It was mentioned that the flywheel had grinding marks. When a good working clutch is taken apart the surfaces will be polished smooth. Chattering is caused by the surfaces trying to grab instead of slipping until the clutch is fully engaged. Compatability of the surface finish and the lining material is critical to smooth operation much like disc brake rotors. I would try to improve the finish on the flywheel and pressure plate and clean well and break it in like Bill said.
As someone that has worked on alot of stuff over the years I have to say you can really make yourself crazy if you get too carried away with dial indicators and micrometers and such. These cars are very simple and can tolerate alot of runout or imbalance and still function pretty well. Most problems like this ultimately trace back to china and subpar aftermarket parts.

[BRENT in 10-uh-C]

Originally Posted by roy green coupe

I think Bill is on to something here. I have also had the experience of a new disc and pressure plate needing some wear to work smoothly. It was mentioned that the flywheel had grinding marks. When a good working clutch is taken apart the surfaces will be polished smooth. Chattering is caused by the surfaces trying to grab instead of slipping until the clutch is fully engaged. Compatability of the surface finish and the lining material is critical to smooth operation much like disc brake rotors. I would try to improve the finish on the flywheel and pressure plate and clean well and break it in like Bill said.

As someone that has worked on alot of stuff over the years I have to say you can really make yourself crazy if you get too carried away with dial indicators and micrometers and such. These cars are very simple and can tolerate alot of runout or imbalance and still function pretty well. Most problems like this ultimately trace back to china and subpar aftermarket parts.

This vehicle has about 2,000 miles since a frame-up restoration and the problem is still there, -so I'm not sure Bill's thoughts are truly applicable in this situation, as surely it has been driven enough to cure this by now. Additionally, can you imagine the response that a new Ford owner would get it they brought their new Ford automobile back due to chatter and the mechanic told them to use Bill's method to repair it?

I also want to make sure I understand what you are saying. You are saying that 'chatter' is caused by rough surfaces? I can believe that a 'grabbing' clutch would be caused by this but not one that shudders. My experiences with a shuddering or chattering clutch has been that the disc is not within the centerline of the spinning flywheel which causes the disc to momentarily spin eccentrically until it can work itself to be concentric. Generally the causes of this is any one or combination of a worn input shaft tip, a worn pilot bearing, a worn front transmission bearing, or a grossly misaligned flywheel housing, HOWEVER generally speaking, when those symptom are found, the transmission will generally jump out of 2nd or High gear on deceleration. This vehicle did not do this, which is partially why we have been puzzled. You may very well be right, but I guess I need to think on that one for a day or two.


So based on thoughts above, it seems most feel like it is the clutch disc. I will look it over on Monday to see if something is obviously wrong. I am pretty sure I do not have a copy of a print of the disc, ...and even at that I would specifically need several prints including the hub, and the plate itself. I am wondering if the repro discs that are having issues are found to have too large of tolerances in the hub area where the disc has a sloppy fit on the main gear (input) shaft splines? I am wondering exactly is different causing them to chatter?

[roy green coupe]

I could be wrong but I thought original ford discs had solid hubs with no cushion springs. I dont think that a person should have to break in the clutch but if the surfaces are too rough it might be a solution. Bills method accelerates the process. The combination of a disc grabbing and slipping compounded by the hub springs recoiling is what I am describing. For the clutch to work properly it needs to slip smoothly at the beginning of engagement.

[Terry, NJ]

FWIW, When I was doing my fly wheel Lightening act. I tried for a 0-0 set up in a universal chuck. The chuck was worn and it required shimming (About .002 IIRC) I managed to get it pretty close. So close that it only required about a 5/16 X 5/16 hole to rebalance the fly wheel. Estimate the weight of a cast iron plug .312 X .312. It ain't much! So for me, Indicating the flywheel as closely as possible is the answer, The clutch face, I don't know! I never had the issue. Tom W. says he get good results with a palm sander. I can appreciate how Bill W's solution might seem realistic to an owner, but not really feasible for a professional restorer. Paying customers don't want to hear "Just drive it for a while and it may get better!", however well the advise may be. Good luck with it!
Terry

[1931 flamingo]

How many miles on this disk?? From where??
You might try contacting : Fort Wayne Clutch, and try a new disk. FWIW JMO
Paul in CT

[Phil Brown]

If your flywheel mounting surface and clutch face surface are not parallel its going to chatter. Or if you have got high and low areas on the clutch face side of the flywheel the highs hit the disk first during the engagement and chatter.
No burrs on the end of the crank or under the flywheel holding it from mating together flat ?
I would surface it and not worry about and VERY small imbalance that it might create because driving ANYTHING with a clutch that chatters is NO fun
If you feel like doing the math a 1" dia slug of steel 1/8" long is 13 grams

[robib]

Flamingo is on the right track, Fort Wayne is excellent. Many clutch discs today are made with not enough "air gap". The gap I am speaking of the gap between the clutch disc itself and the friction material. There is a marcel spring between the disc and the friction material which is there to "soften/dampen" clutch engagement, preventing chatter. Good friend built an A with a flathead and 5speed. Chattered so bad he could not drive it. Called Fort Wayne, they sent a new clutch disc and all is well.

[BRENT in 10-uh-C]

Originally Posted by robib

Flamingo is on the right track, Fort Wayne is excellent. Many clutch discs today are made with not enough "air gap". The gap I am speaking of the gap between the clutch disc itself and the friction material. There is a marcel spring between the disc and the friction material which is there to "soften/dampen" clutch engagement, preventing chatter. Good friend built an A with a flathead and 5speed. Chattered so bad he could not drive it. Called Fort Wayne, they sent a new clutch disc and all is well.

I have dealt with Ft Wayne clutch on numerous occasions, and you both are correct on their expertise.

I will do some research on this 'air gap' that you are mentioning.

[KR500]

I agree with some as to the disc possibly causing the chatter. If a disc became overheated and weakened the torsional springs or if the springs were never up to tension in the first place, I would want to try a different disc. I was under the impression that a clutch disc should be included in the balancing job when doing the pressure plate and flywheel. If you have ever driven a vehicle with an oil or grease soaked disc you know how they can chatter.

[Dick Steinkamp]

Originally Posted by KR500

I was under the impression that a clutch disc should be included in the balancing job when doing the pressure plate and flywheel.

The disc ends up in a different position every time the the clutch is engaged. How would it be done to balance it with the PP and flywheel?