Technical Clutch Judder / Chatter again!

[Tin Tin]

Hello to all,

I am still trying to resolve the clutch judder / chatter which my car seems to suffer from. Although it has improved since I last changed the clutch, its still there so I have taken the engine out once more to investigate and my suspicions are that an oversized Pilot bearing may be the cause.


To me there is far too much slack on the pilot bearing and input shaft. Both items are new but it's possible the internal dimensions of the bearing are too large. My measurements of the input shaft is a diameter of 12 mm but this will be measured using Vernier calliper a not a micrometer.

I have attached a video showing the play on the input shaft bearing and would be grateful for anyone's thoughts?

If this is not the cause of the clutch judder then I plan to inspect the rear suspension for worn bushes as I can't think what else can be the cause.

All help and suggestions appreciated.



Peter

 

[dan00090]

Did you have the flywheel turned? It gets hot spots that need to be machined out.

 

[Tin Tin]

Thanks Dan,

I think the fly wheel is OK, I am not a trained eye but can't see anything untowards.

By way of back ground, when the car had a 500 engine & transmission it had clutch judder.

It now has a 650 engine and transmission and still has clutch judder, all engine and transmission mounts have been replaced.

This makes me think could it be nothing to do with the engine and transmission and be caused by worn rear

suspension bushes. I do not know how likely this is?

In order to take the load off the suspension and check the bushes for wear I need to remove the rear dampers however the damper locking nuts are rusted solid and need to be cut off, but before attacking this as a cause I want to make sure that I'm not barking up the wrong tree and it is the slack on the pilot bush that is causing the problem.

 

[Goldnrust]

I have only secondhand information, but if you search the forums for clutch judder you will find many posts discussing the clutch cable mounting at the gearbox end, and there is an apparently easily made mistake with a bracket location which causes judder issues.

Might be worth a look!

Edit, it was suggesting one of the threads I’d previous read at the bottom of the page! https://www.fiatforum.com/threads/clutch-chatter-mystery.299236/

 

[the hobbler]

I have only secondhand information, but if you search the forums for clutch judder you will find many posts discussing the clutch cable mounting at the gearbox end, and there is an apparently easily made mistake with a bracket location which causes judder issues.

Might be worth a look!

Edit, it was suggesting one of the threads I’d previous read at the bottom of the page! https://www.fiatforum.com/threads/clutch-chatter-mystery.299236/

The bracket for securing the clutch cable is part of the cable outer. It goes round the cable and has a curved extension---this extension fits into a casting on the side of the gearbox. The casting has 2 small horizontal bars--the end of the clutch cable securing bracket fits over an adjacent stud and then the end of the extension goes in between the 2 horizontal bars.

 

[Tin Tin]

Thanks all and much appreciated to receive your thoughts & guidance.

Although everything is dismantled, I think I have the correct cable which was secured to the gearbox using the Brass nut shown in the picture.

Assuming the cable is correct and was correctly fitted with the bottom of cable bracket located in the slot / 2 horizontal bars, I believe this is fine but happy to be advised.

Do I take it that I should not be unduly concerned with loos fit of the Pilot Bush?

Could wear in the rear suspension trailer arm cause symptoms similar to Clutch Judder?

What am I missing?

Looking forward to you thoughts.

 

[the hobbler]

Thanks all and much appreciated to receive your thoughts & guidance.

Although everything is dismantled, I think I have the correct cable which was secured to the gearbox using the Brass nut shown in the picture.

View attachment 405444View attachment 405445



Assuming the cable is correct and was correctly fitted with the bottom of cable bracket located in the slot / 2 horizontal bars, I believe this is fine but happy to be advised.

Do I take it that I should not be unduly concerned with loos fit of the Pilot Bush?

Could wear in the rear suspension trailer arm cause symptoms similar to Clutch Judder?

What am I missing?

Looking forward to you thoughts.

You are correct in thinking that the bottom of the clutch cable bracket fits in between the 2 small bars under the brass nut, and that the brass nut secures the bracket to the side of the gearbox. How loose is the fit of the pilot bush---is the bush itselfloose in the endof the crank or,is the spigot shaft loose in the bush. The bush can be obtained as a seperate part and can be (fairly!) easily removed from the crank.

 

[Tin Tin]

The pilot Bush has a good interference fit in the crankshaft and is secure. Both pilot bush and shaft are new, but the fit between them, in my opinion, is loose as shown in the video.

I was a little concerned at the looseness of the pilot bush on the shaft however I went ahead and fitted them both hoping all was good, which turned out not to be the case hence removing the engine and transmission for a second time.

Hopefully the video shows the slack between pilot bush and spigot shaft.

I will be replacing the pilot bush with another new one from a different source and hope that the replacement part will have a much closer fit.

My quandary is, is the clutch judder caused by the bad fit of the current pilot bush or could trailing bushes also cause the problem if they turn out to be worn.

 

[plasticpig1972]

Tin Tin,
please get your Flywheel resurfaced even if the surface looks good. Sometimes they are nice and shiney but not flat concave or convex.
Always when fitting new Clutch resurface Flywheel.
Good luck
Alan

 

[the hobbler]

Tin Tin,
please get your Flywheel resurfaced even if the surface looks good. Sometimes they are nice and shiney but not flat concave or convex.
Always when fitting new Clutch resurface Flywheel.
Good luck
Alan

Alan's suggestion is a wise one---even though the flywheel looks fine, it would lose you nothing to have the friction surface 'just skimmed'---just enough to guarentee that it is flat.

 

[Tin Tin]

Many thanks for the suggestion, i will have to hunt around to find someone in Southeast that can do that as, as each year goes by there are less and less old fashion machine shops around.

One point I realise I’ve missed in my description Is that the judder only occurs under load. If it’s just me in the car on the flat then I can pull away at a slow speed with no problem. It only seems to occur going going uphill from the rest or when there’s two or three people in the car .

Time to investigate local machine shops.

 

[the hobbler]

Many thanks for the suggestion, i will have to hunt around to find someone in Southeast that can do that as, as each year goes by there are less and less old fashion machine shops around.

One point I realise I’ve missed in my description Is that the judder only occurs under load. If it’s just me in the car on the flat then I can pull away at a slow speed with no problem. It only seems to occur going going uphill from the rest or when there’s two or three people in the car .

Time to investigate local machine shops.

Why not have a word with somebody like "Ricambio" or "Proietti" to see who they use. They do complete car restorations, which must include 'engine jobs'.

 

[Toshi 975]

What about simply trying a different flywheel?

 

[the hobbler]

What about simply trying a different flywheel?

A different flywheel may well be the answer---but DEFINATELY have the friction surface skimmed.

 

[Tin Tin]

There is certainly no harm in trying getting the flywheel skimmed.

It’s just really strange that the car has now had two different engines each with its own transmission and the problem persistsHence my fear that I may be barking up the wrong tree.

A different flywheel may well be the answer---but DEFINATELY have the friction surface skimmed.

 

[Tin Tin]

Thank you for all your suggestions and I will explore getting the flywheel skimmed.

Will keep you posted of developments.