348 CLUTCH TROUBLE

I agree however, I have taken one bellhouse off that was improperly placed I suspect by placing the enitre pumpkin on the shafts instead of the flywheel assembly first then bellhouse on that sliding on the big bearing. What happened was the mechanic forced the cover and assembly guts on the shaft. This caused the lockring on the input shaft to slip off. The grubscrew was placed too far in and that caused the internal flywheel assembly to put too much pressure forcing the fingers onto the throwout bearing too much. While the bearing was good the extra pressure wore grooves about half way through the fingers. So I was not able to save the pressure plate and just resurface the discs for cheap but my friend had to buy an entire new assembly. So while the pictures make it look like a slam dunk you can still screw up the install. I believe this does effect the freeplay and it felt funny to drive. I wish I had pictures it was before the day of digital cameras. Personally, I have never tried to adjust the clutch from the grubscrew. I only note that it can alter the flywheel assembly and do agree that if you are not reasonably fully seating in the bearing you get vibration etc... The grubscrew can only effect a minor distance change anyway since the internal guts will hit other stuff of break other things as in the case described above. Additionally, I don't think you can place the flywheel assembly into the big bearing without getting mostly fully seated because then other things would not fit but I have not tried to do it wrong. There seems to be plenty of factory built in range of operation with 4mm of set-up height play vs, a wear limit of 1.5mm on the plates. So I don't think adjustment is really an issue other than to note that the assembly can be moved anymore than the clutch shim packs being less than say a 0.5,mm really does much for increased spring clamping load. It is more likely that the clutch design is somewhat if not outright "centrifugal" and that the significant clamping loads come from there. Racers may feel the extra 0.5mm but for the street guys it does not matter. I have not taken apart nor examined this area in a while to remember if my speculation is waranted nor have I calculated the clamp load differences with or without shims. I do believe that the reason for this grubscrew is either, minor movement of flywheel assembly, manufacturing ease, your idea of preload. I do not think there is anyway that this screw helps lock the big nut. In fact the measured snout length of the tail of the flywheel is a fraction more than the thickness of the inner race. Additionally, the big nut is stepped to lock on the inner race but not put pressure anywhere outside of the inner race. I could buy the idea of the grubscrew as a lock to position the big nut so it does not put undue forces trying to pull the inner race out of line with the outter race only if the snout was smaller than the race width. But then It would be just easier to use a bearing of the correct width than make a kluge like the grubscrew and not tell anyone about it.

 

O.K. the torque spec is not anywhere in the WSM. Personally, I use 150ft-lbs in my impact gun. My gun has a 500ftlb reverse and it takes a couple pulses to get this nut off so it is on there tight and 150 ftlb is not unreasonable for this size nut. gearbox shaft ringnuts are similar torque spec and my number seems reasonable. I alwasy use some 271 locktite because 1) I do not want things coming apart and 2) you can really get the old parts clean like the very 1st assembly in the facotry where 242 locktite is more appropriote.

I took the cap off and the grubscrew is 12mm 1.25 pitch. Smith says the torque on a 12.9 class 12mm is 79ftlbs . The 105 you quote may be from Nm spec. Smith says 108 Nm or 79ftlbs. I have no way to know if this is a 12.9 class. Based on the quality of other Ferrari ringnuts I suspect a lower class which means less torque than 79ftlbs. There is no reason and it is not likely that Ferrari would spend extra to put a higher class small screw in a lower class softer big screw. It just don't make sence... What are you talking about half nut? I don't understand. I see no difference in design parameters vs. a simple bolt with hex nut. I think what makes a fastner work is thread pitch, contact , surface area and remaining tension stress for lasting clamping force. And you are more likely to keep proper clamping forces over the surface area of the threads in the big nut on the flywheel snout than you are by maintaining that same clamping force/ tension stress by pressing on the 12mm round tip of the grubscrew via a free floating not fully supported end cap. No science just my thinking.

 

No Doubt, you are really trying to stir the pot or you need to read this thread again slowly or I'm really sorry because I just have not got my point across and Ferrarifixer has not got his across either. I'll answer as best I can you specific points and maybe Ferrarifixer will too.

<<1. Max torque on the 60mm flywheel bolt is unlimited due to the land. Crank her down as tight as you want (heh, heh, this should stir the pot).>>

I say 150ft lbs no documentation to back me up. 308 lay and mainshaft I have a Ferrari spec in writing it is 140ftlbs.


<<2. the inner hex grub nut **does** move the flywheel position a little (up to 7mm), but there is still some debate if that will typically extend clutch life.>>

Yes but you can't move it 7mm because other things hit. There is not reason to move the wheel if you have a proper good flywheel assembly and I and Ferrari do not recommend that you try to move it in other than the factory position.


<<3. It isn't dangerous to tighten up the inner hex grub nut (e.g. to extend clutch life by moving the flywheel closer to the throw out bearing).>>

Unknown. It can be done but there is no reason.


<<4. 348 clutch life can be extended (presuming non-damaged flywheel fingers, incomplete pad wear, etc.) by removing the clutch pack shims (though a picture of this being done may be difficult to find).>>

I think shims where placed during manufacture to build in a manufactured "set-up height". I have no evidence. For all I know these could be here as anti vibration shims like in your brake pads. Clamping forces are increased by their removal. It is unknown how much force is increased. They have nothing to do with clutch life.


<<5. 348 flywheels can be run without any flywheel grease, and in fact run better with no grease than with half grease. Full grease is OK, too.>>

NO. Full grease = no rattles = proper starting. Flywheel rattles talk to the TDC sensor and cause poor or no starting especially hot starts. If you take all the grease out there is a whole process of mods you have to do to get the system to work. I have done it and it works. The car starts 100% of the time, does not rattle, and does not destroy the gearbox from vibration because you now do not have a voigth dampend flywheel. I have 5 years of track use only on such a system. So that is my only data point on that.

 

The shims are used to RESTORE set up height.

As the clutch wears, the set up height changes/increases (the fingers rise away from the flywheel).

When the shims are removed, the clamp is restored and the fingers will move into the flywheel.

Different thickness shims can be used (thinner), or simply remove them, whatever works.

 

I cannot see any other position that this flywheel could safely be in?

The flywheel support bearing #55 is in a static axial position located in the bell housing and should be retained in this position under assembly. The shoulder of the flywheel snout can only be up against the face of the inner race of the flywheel support bearing once the flywheel bolt is fully tightened up & thus making the flywheel being only fixed in one true position.

Are we all agreeing with this!! ??

Paul

 

When I did my 348 clutch I needed air tools to get the large nut off. This was done with the help of the guys at the local tyre garage.

However, when I put it all back I did make a potentially catastrophic mistake in that prior to taking it back to the tyre shop I torqued up the large hex nut with just a hand held impact driver like the ones used for tight screws etc.

When I put it all back and started it up the rear of the clutch assembly scored the bell housing. A very frightening moment and horrible noise.

I do not know to this day if the little grub screw was incorrectly positioned or it was just lack of torque suffice to say after the visit to the tyre shop and use of there air tools she worked fine when refitted to the car.

As a side note, the SUH settings were pre-set in the clutch assembly received when I got it from Ferrari (AP dual plate clutch)

So, in short, make sure that large nut is fully torqued up when it all goes back. I have heared 150ftlbs but don't know if this is the correct value.

 

Hey mate, isn't that racer a bit old to be wrenching?! Ha!

 

For the record:

206Nm / 152 lb/ft is the official torque of the flywheel nut ( Source - Ferrari UK Technical)

Paul

 

I'm a bit confused about John's description of his problem in post 108. The only way the flywheel can hit on the bellhousing is if the bearing isn't fully pressed into the bellhousing. When you tighten the ring nut, it will draw the flywheel hub all the way onto the inner race of the bearing, but it won't draw the bearing any further into the bellhousing.

I don't think John's problem was a loose ring nut. I think his problem was that the bearing wasn't seating in the bellhousing. Perhaps it WAS seated properly, but when the flywheel was reinstalled, it pushed the bearing off the shoulder on the bellhousing so that it was no longer seated.

In any case, wouldn't the problem have been apparent when spinning the flywheel by hand, before reinstalling the clutch assembly onto the transmission and starting the car?

 

The only way the flywheel (green - spinning) can hit the bellhousing (pink -stationary) is if the bearing (blue) is not seated all the way against the shoulder in the bellhousing. It doesn't matter how tight the ring nut (orange) is. The ring nut can only pull the hub on the flywheel further onto the bearing. It can't push the bearing further into the bellhousing if the bearing isn't seated. That's the way I see it.
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we are having a similar problem with a lusso...

 

ROLOcr,

I come down to fix the lusso. You find me the hot flyfishing guide to take me roster fishing! Costa Rica has teh best Rosters in the world. Did you know that?

 

haha, the lusso is from one of our costumers, we work with exotic cars, just that lately we have been very busy and haven't had any time to check out the problem,
you can come to COSTA RICA and i'll assist you in any way i can! do you want me to help you?

email me [email protected]

 

I had the same problem that FERRARI 348 posted - one of those clutch spring broken and just recently replaced the assembly.

Curious what the typical life of the cover - anyone had similar experience?
(I could not find clutch replacement in service record so can not tell if the broken one came from the original car or replaced at some point of 15 years. I owned it for 4 years and drove 25000 miles - guess life is certainly longer than those....)

Mine had serial number of #5557, that was not very far from #5460 that I read from pic posted by FERRARI 348...

Yoshio - Japan
1990 348ts
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We hope fully might be somewhere towards a conclusion on the bolt. I did actually talk to Ferrari Tech about this grub screw and they do not have any procedure on how this works in conjunction with the flywheel bolt.
Without further a do, I decided to contact the very knowledgeable Bill Eccles form www.boltscience.com who gave the following reply to my question.

********
Hi Paul

Yes I agree that the screw (#57) would appear to being used as a means of preventing the adapter (#56) from self-loosening. I have not seen such an arrangement tested and so I am not sure of the effectiveness of the method.

Best regards

Bill Eccles
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I think we can hopefully put this one to bed now knowing that the flywheel bolt needs to be torqued up to 206 Nm and the grub screw nipped up to aid the locking of the flywheel bolt.

Paul

 

I know the guy is an expert and I just a fat old billybob bit I don't buy it. That littel nut as a lock is like the myth of sticking you finger in a gun barrel and Elmer Fudd gets the backfire in his face. Fasteners lock up due to the dynamics of how a thread works. Fasteners ability to lock-up or hold a specfic torque is related to metal selection, thread type , and thread pitch, and size relative to the torque it has to hold. We keep calling it a "little grub screw" because it is little. It ain't locking anything and for sure makes no sence that it would lock anything if you just "nip it up a bit". The fractional amount that small screw could add relative to the surface area of the large nut is insignificant.

 

That tool looks great but I REALLY like the countertops!

 

we made a similar one to remove the nut from the wheel hub to remove the wheel bearings in an F40

 

i've seen these "bolt within a bolt" things before in electic motors.

the 'small bolt' is not meant as a means to secure the main bolt.

Its invariably there to set travel.

ie , loosen the 'small bolt' , tighten up the main bolt , then tighten
the small-bolt up to contact and then back off.

my totally worthless 2 cents.