348 CLUTCH TROUBLE

Thanks Pap.

What is the official torque on the lock setscrew?

 

Well, IIRC it is a 12mm machine screw and probably "10" grade, so according to standard charts it should be torqued to 85 ft. lbs.

 

Considering what that set screw bottoms out against, I would be VERY wary about attempting to torque it down to anywhere near 85 ft/lbs. That can't be right. The THREADS may be able to take that much torque, but I think the spacer and/or the land on the flywheel would fracture under that much pressure on a small surface.

 

I agree, however, it should be firmly torqued - I think 50 ft. lbs. is about right.

I know you are joking, but the whole point of the "grub screw" is to lock the ring nut in place. That is the one that could come loose if the grub screw got loose. The ring nut could come loose because 150 ft lbs is way under the recommended torque for a tread of it's size - IIRC 25mm. That is why Ferrari implemented this design - so that the ring nut could be "under-torqued" and still never ever move. It is a very slick little piece of engineering - I am saddened that many of the brotherhood have so misconstrued its beauty, and put a lot of bad information out on the net. Especially where people say not to touch the grub screw before removing the ring nut. That piece of misinformation causes more grief for nothing than, well, let's put it this way - it's not really giving organized religion any competition, but they noticed!

 

I don't think you will either. That was my whole point: in my analysis of this mechanism I see it as a very, very failsafe system. 152 ftlbs is plenty to correctly lock the flywheel into the bearing. Then the way the lock set screw and plug function to put a load on the ring nut's threads ensures that the ring nut won't come loose. I didn't put mine up to spec either, used some locktite, and I'm not worried a bit, although next time I have the exhaust off, I am going to undo the set screw and ring nut, and then torque them to spec.

My difficulty was finding a way to hold the flywheel while torquing it. (Undoing with the impact drive was much easier.) Now I realize that all you have to do is get the ringnut and setscrew reasonably snug, leave the cover off, install the flywheel in the car, put her in 1st, set the handbrake, and then you can remove the set screw and ring nut, apply locktite to the ringnut, torque it, apply locktite to the set screw, torque it, and put the cover on. Much more sensible I think. Anyone see a problem with that procedure?

 

That would be me. This is my story and I am sticking too it. The last 8 pages where I have posted and shown you pictures pretty much lays it all out in living color. This dead horse has long been beaten. I think you need to blow smoke in a different direction and play in an area where you know you can win.

 

Well, Ferrari was apparently so proud of the "beauty" of their set-screw arrangement that they totally failed to give it any mention in their workshop manual. Not a word. Nothing about its function, nothing about its assembly, nothing about its specifications.

Of course, they also failed to mention that the flywheel could be opened and regreased, but at least they took the trouble to give an incorrect figure for the quantity of grease to be used.

 

A very simple experiment could establish the truth or falsehood of your and my stories.

Setup:
1. Put car in 1st gear.
2. Set handbrake.
3. Remove exhaust.
4. Remove cover plate.
5. Remove setscrew.
6. Loosen ring nut.
7. Tighten ring nut to torque of 150 ft. lbs.
8. Replace and tighten setscrew to torque of 50 ft. lbs.

Experiment:
A. Get the biggest torque wrench you can find and see if you can remove the ring nut with it - if so determine the torque required to remove the ring nut.
(stop at about 350 ft. lbs. - you don't want to break your drive train.)
B. If you were able to loosen the ring nut, repeat the Setup. Now loosen the setscrew, and take a reading per step A.

If you are correct, the torques observed to loosen the ring nut should be about the same.
If I am correct, the torque needed to loosen the ring nut should be much greater for step A than step B.

Well sir? Is that a valid experiment or not?

 

You missed my description of my brake cleaner fueled hallucination where Enzo himself came down from heaven and was laughing about how the English speaking mechanics sooner or later make mistakes because they want to believe what they hear instead of what they see. And how the manuals always have errors because his engineers don't really care what the gringos do with the cars. Enzo said "gringo!"

 

This is not a dead horse. As long as people are wasting time and money because they read in the midst of otherwise correct information, "...now remove the ring nut. Don't touch the set screw, because that...", this horse is still in misery. I was a victim, and I am trying to prevent new brothers going through what I went through.

 

Uh-huh. What about that one FBB? What a coincidence that 225 ft. lbs. is just about the correct torque for the ring nut's thread size. In other words this slick little piece of engineering makes the ring nut as secure as if you had torqued it to the max, only you don't have to. Sweet!

 

NO it is not valid and I have done it. I take the big nut off all the time just with an impact wrench with no regard to the grub screw. Furthermore your earlier post about how to hold the flywheel and torque it since it free wheels demonstrates a pretty glaring absence of mechanical know how which in regard to this issue implies you are making assumptions with no fact or semblance of mechanical knowledge to make me think you could be correct. Finally, you can and I have driven the car without that grubscrew in race conditions with no ill effects of large nut loosening. Those are facts. As I have said before this issue is beating sand into glass. Sometimes we can speculate and argue about what ferrari's intentions are but that does not mean we can't fix it. People are making a big deal out of this little screw.

 

So what? That makes perfect sence that removal torque is added with a second fastener. That is just an engineering fact but there is no way to know if that is the intended result. As Miltonian notes the WSM is silent on their supossed "genius". I can and have proved the car can be run quite hard without the little nut. Ferrari are the laziest guys on the planet as can be verified by looking at your wiring, or gearbox. Do you really think Ferrari would take the time to design a two step locking mechanism and the time to assemble it when those lazy SOB's could just click the impact wrench up one click and just ram it home for 225 ft lbs? Ferrari is so lazy they won't even take the time to stake the lockrings in your gearbox and you think they are going to make a two step fastner? You guys are way over thinking the problem. Maybe the automotive press got it wrong the 348 is the best Ferrari ever engineered.

 

Slick??? That's just obvious like you can run safety wire through a little hole in a bolt and keep a nut on. I guess it is "slick" if you never seen it before. They also make rubber things that go across your windows now for when it rains.

 

Look, you are absolutely correct; we have no idea what this was "intended" for. Hell, the person who designed it may not even be alive. My concern though is the numerous places in how-tos linked from the 348 primer and other brotherhood resources that give very bad advice in relation to it.

They say "do not remove the setscrew before removing the ring nut." That is nonsense. (I almost stripped my ring nut before a professional Ferrari mechanic of long experience stopped me and removed the setscrew. Then the ring nut came right out.)

They say "the setscrew adjusts preload, and should not be touched." More nonsense.

They imply that one should remove the ring nut, and then re-install the ring nut, leaving the set screw untouched the entire time, and that dear sir is not just nonsense, it is dangerous nonsense. One would be far better off to do what you have done on occasion and leave the thing out entirely.

What you, I, or anyone else thinks it was intended for is meaningless. What is important is that people do not get bad or dangerous advice.

To that end, I contend that the best, i.e. least likely to lead to harm, way to talk about it is as a lock setscrew no matter whether it "really" is or isn't one. Just like with any other locking fastener, the locking feature may not be required for successful functioning of the mechanism, however by so characterizing it, no one will be likely to mistake its methods of employment and do something unnecessarily costly or dangerous. (e.g. utilize the secondary fastener for the primary attachment.) Is that too much to ask my friend? That we speak of it in a way that will minimize harm?

If you have a better idea for what to call it, please share.

 

I thought I was asking for constructive advice and comments in reference to that. My procedure is an just idea that I am wondering about. I don't see anything wrong with it, but that is why I asked, maybe somebody else sees something I don't. The fastener is being torqued to 150 ft lbs. with a torque wrench. The engine puts out, what, close to 300 ft lbs? I was not suggesting that anyone use an impact driver in that scenario. If you think it's not a good idea, or if you have a sure fire easy peasy way to lock the flywheel while torquing it, I am all ears.

 

from my point of view the intention is to adjust the axial clearance of the clutch shaft with this screw ?

 

First let me say I do not want to bash you and don't want to sound like I am. My problem is not "what" you have said in as much as the dogmatic pontification. Some of the things you have said are just false. There are many ways to do things. For example I can't even remember how many of these clutchs I have done and i have never had to take the grub screw out first and never will. The face that an FNA mechanic did that shows that he understands the fastener and that removing the small screw can lighten pressure on the big one to some degree. If you bung up the grooves in the big nut your choice is to do as he has done and or cut the thing off. If you have a really frozen big nut and a really frozen small screw we can all agree that the small screw even if 12.9 class could be ripped apart by an impact gun and leave you with heat and cutting as a solution. This event you have experienced is just common everyday mechanics that good mechanics do to save themselves time. This event is not "the" way it should be done.

You have no basis for calling anything dangerous as there is no danger. You in fact can put the big nut on with the little screw part way out, completely out, before the little screw, after the little screw with zero effect on the final outcome as has been done by not only myself but others right here on Fchat.


And finally, I am sorry but it is difficult for you to have credibility when part of a post asks how to torque the bignut which is below the understanding of what the little nut does. It is like talking forcefully about integral calculus but not knowing what algebra is.

I think that if you reopened this thread and said hey guys I had problems getting the big nut off and if you lossen the little screw it may help that's one thing. But to call ideas bad, dangerous and claim to understand Ferrari's "intended" design with not much knowledge to back that up is a bit of a stretch.

 

If the setscrew happened to be extending out enough from the ring nut so that it contacts the little plate before the ring nut has fully secured the flywheel's boss into the bearing, that would have the potential to be dangerous. I admit it is unlikely that anything seriously bad would result, however it would be very poor practice to operate in that sequence. The setscrew should always be retracted enough inside the ring nut that there is no chance of this happening when the ring nut is torqued. The easiest way to make certain that this is the case is simply to remove the setscrew before torquing the ring nut.

FBB, I feel insulted by your holier-than-thou attitude. You apologize, and then proceed to explain why it was OK for you to get so rude. Yes, I pontificated and I shouldn't do that, but let me give you a little hint: the best way to deflate a pontiff is to prove him wrong. You can't because in this case you are wrong. You have years and years of experience with these cars, but for whatever reason instead of wanting to share that experience in a helpful and respectful way, you want people to respect your experience and the insights thereby gained, but you get very rude and defensive when someone questions one of your statements. And god help them if, with simple logic and knowledge of physics they have the nerve to tell you that you are wrong. For you are wrong here. Most abysmally wrong:

1. Any locking fastener can be removed without "unlocking" it first - you can shear cotter pins if you want to - that makes no sense at all.

2. Many locking fasteners can be installed "pre-locked", but then you run the risk that what it is fastening is not fully secured - you can cinch a lock nut to its nut and then run the pair up to the item being clamped - and this also makes no sense.

I am wrong too. I should not have reopened this thread, and I should have tried to avoid pontificating. I hope I have learned my lesson.