348 CLUTCH TROUBLE

I try not to be a leach...I try to give back a little of what I get from/to the 348 Brotherhood. Everyone is so helpful with tips that I'd feel like a slacker if I didn't give a little back.

That being said, my wording probably did cause this whole shindig, though I assure you that it was inadvertent. Apologies.

Anyway, have we all reached the same conclusion after all of the dust has settled?

1. The hexscrew/grub really does adjust the flywheel position a little, and really could add a few miles to a dying 348 clutch, or not?

2. Such an operation is dangerous or not?

If there is blame to go around, then the fingers should probably be pointed at me (though my heart was in the right place as I was trying to help an honest bloke out a bit). But blame, whether mine or not, doesn't help the 348 Brotherhood.

On the other hand, if all of the 348 experts agree on the above potential clutch adjustment/danger, then *that* could help the 348 Brotherhood going forward.

Ha! So even if I started this whole thing in error (or not), some good could come from it.

Are we in final agreement on the clutch adjustment or not, then?!

And in the spirit of the holidays and the 348 Brotherhood, hopefully no one will have any hard feelings. I do admit that I make mistakes, after all!

 

Hmmm. I can see how the flywheel could be set wrong initially, shortening clutch life... and then how it could be set correctly to prolong it a little. But if set correctly in the first place, there is nothing you can do to prolong it's life.... apart from removing the shims in the clutch pack.

 

If you wanna make an omlet, your gonna have to break some eggs. We all get our chops busted around here. Rifledriver and I had a very good debate going in the "$16k part" thread. So don't worry about it.

Besides, all the info you put on your website is a great help for the brotherhood.

 

Cool. I'd hate to be known as the guy who screwed up the 348 Brotherhood or some such.

I had no ill intentions; what I said in that first post (really, 2nd) was an honest effort at helping. And since I personally haven't used that 348 clutch "tip," I couldn't argue for it when corrected (without looking like a dweeb, anyway).

 

OK. Would it be accurate to say that in some types of 348 clutch failures, that one could safely remove clutch pack shims to give a few more miles of life to said clutch (say, while waiting for a part to be ordered/shipped/arrive)?

 

I'll share one of my favorite quotes with you.

"Arguing on the internet is like running a race in the special
olympics, even if you win, you're still a retard."

 

Joe,

I run without a roof so the sun is right in the cabin. Can you see the led's in direct sunlight? I like the lowtech analog on my stock gages since I can glance and know where I am. Being a hillbilly I don't read so well. Don't you have a vette too? Your name seems familliar. I'm in Torrance. I'm more interested in going Motec and turbo. Programing the system to work has got me scared. They say it is easy but I am computer impaired. Interested in a little programing fun? Motec in HB, Ca. just does not make me feel warm and fuzzy but they sure are willing to sell me the product.

 

No, its an H pattern, not sequential.

And there is NOT a differential. It's a locked spool.

Dinosaurs... but hey, Jurassic Park was good movie!

 

Yes, absolutely. Just check the centre plates are not worn to the rivets, if ok, remove shims and go again. Could double life in some cases.

 

Yep, no problem FBB, that was the office I worked at for so long... I can tune your engine but it tends to get expensive once you add up the cost of the harnees, ECU and sensors. When I did my 911 turbo, I had over $10,000.00 in the MoTeC system (and I worked there). Proper engine control will gain better torque off the corners but in all honesty, maybe 2 seconds off your laptimes. I can get you 3 seconds in 1 day of proper chassis tuning and driver developement for .250 the cost... Let me know when you want to discuss your project, I would love to be involved. Maybe a SoCal F-Chat project!

Oh yeah, we are going to have to convert you from your analog thinking...

 

I'll look you up when I get further. And about that thinking...mine is suspect. I am happy to be able to think at all. I'm glad to have a 12 year old or all my digital clocks would be flashing "12".

 

I hate to admit it, I like to think that I am fairly knowledgeable, but what in the world are "clutch pack shims"? On a 348?

 

The clutch has shims when built form new. They set clamping load. They space out the cover plate away from the flywheel surface.

As the clutch wears, the clamp load reduces. When it starts to slip, the shims can be removed and clamp load is restored.

In reality, it's hard to perform this with any warranty though, so it's a DIY job.

Most 348's I've done, have already had the shims removed. The one I did last week still had them though.

 

LOL! I can help...

 

IMO - Looking from the exploded diagram the socket grub screw is used to lock the flywheel nut and nothing else - I have seen this method before but can not think for the life of me where - something tells me it was on a turret on one of our CNC lathes.

I would have thought that the flywheel bolt would not be torqued up to a colossal amount for fear of distorting the inner race of the DAC bearing hence the grub screw being able to lock the flywheel bolt. (This may also be why a lot of people say that the flywheel bolt is quite difficult to get off - maybe if they loosened the grub screw first?? )


Anyone have the torque setting of the flywheel bolt out of interest?


Paul

 

I diasagree Paul. Fasteners in general take a torque spec proportional to their size and material type. I forget the exact amount of torque on this large nut somewhere about 100 to 150ft lbs range...I'd have to look it up. The grub screw is not designed for that torque as it is too small. It is about a 8mm 1.25 pitch or so. I think the correct way to position this unit is as I posted above. So the grub screw becomes not significant hence my comment above that we are really just pounding sand into glass. I do not know what a DAC bearing is but in general it is extremely hard to damage a race with uniform clamping forces via a fastner. Also, many mechanics just ignor the grbscrew and fire in the large nut at 150ftlbs. This means the point of the screw is jammed in really hard. If you try to remove this without lossening the big nut you rip the 8mm apart. Even a 12.9 class 8mm is only good for about 25-50ftlbs. The big nut is not hard to remove with the right tool either purchased or homemade. Mine is home made and could be a nice little business for you to get into for the DIY'ER. The only other person to make them is Baum tool or FNA as I understand it. FNA tools are either unobtainium or million dollar. Baum makes crappy tools as I have a few and broken a few. My homemade tool work better than theirs and hold up to the abuse better. Now a smart guy like you could CNC some tools with proper heat treatment and you would do a great service to the Ferrari community. Ask Ernie about my hillbilly tools he will laugh. But I don't look so funny when they actually work! I have seen all kinds of bozo ways to get that nut off including mechanics pounding it off with a cold chisel then billing you for a new nut at Ferrari prices. At least when a DIY'ER uses a chisel he knows what he is in for . In my hands one blast of the impact gun and the proper remover tool and it is just not an issue.

 

I know all about the Redneck Tech tools, they work great. I even custom made one while I was a your house. Actually it was fix one, but that's what's great about them, they take a lick'n and keep on tick'n.

 

There is an operational spec for all cluthes call a set up height and usually is from the top of the pressure plate fingers to the face of the flywheel when the unit is assembled. This range acounts for proper functioning of the levers and clutch throughout it's life. Levers have ratios that assist in making your clutch feel heavy or light to your leg. They have ratios like a rocker arm in a valve train. You could have a 5:1 ratio in there I have never measured it. So in the 348 the SUH is a range of 4mm from 47-51mm. The designers put the cover shims in to space the SUH for maximum clutch pack life. Small changes in pack thickness make big changes elsewhere due to the lever effects. There are many factors that effect this operational range such as air gap needed when plates are disengaged, wear limit of 0.8mm per plate, intermediate plate wear and those shims. Those shims are very thin and I can only speculate at their design purpose. I have seen things like to for antivibration like the back of brake pads. There is manufacturing variation in clutch plates especially street cars that use marcels and the shims could be used to make up for that variation to make up the factory delivered new SUH which I have also never measured. I can't remember the inside guts of what the pack looks like but yes if you took the shims out you would increase spring loads to a minor degree on the plates which would be nice in racing perhaps but I do not think street guys would notice. I would need to look at the clutch pak internals to decide if static clamping force is important. Many clutches are designed to be centrifugal. That means as your RPM increases the clamping force increases. This allows easy foot pressure to be used for comfort but massive torque handling abilites as the RPM increase. It is like swinging a rock at the end of a rope...fast spin makes it feel heavier in your hand.

 

Hmm - this is interesting as 2 Ferrari technicians I talked to earlier seem to agree the it is purely for locking the flywheel bolt. (The thread in the middle is not 8mm - I'm sure its a 12mm fine pitch - I haven’t got the drawing to hand at the moment)

Was there an eventual outcome on what every one thought that the grub screw done?

We’ve done the 60mm ring nut tools for about a year now and have saved quite a few knuckles!!

Paul
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O.K. lets say it is a 12. I took it off yesterday in my previous pictures but for get what it is. but a 12mm 12.9 class which this is not likely takes 79 ftlbs per carrol smith. So still no one is going to use this little thing to hold that big thing "it just don't make no sence boy". And it will not lock anything. There are better ways to lock a fastener even stupid ferrari ways. If they entended and threaded the snout they could have keyed it and used a traditional ferrari lockring. don't forget this was not one of ferrari's most thought out projects. I think the updates to the 348 clutch are about version 4 and that does not include multiple throwout bearing upgrades and TSB's on the grease pack amount etc... I mean how difficult is it for a designer to decide how much grease to put in a thing anyway? I don't care how much we all love ferraris they are designed and built by the "low bidder"! Just look at the electrical system or Ernie's $16,000 F1 gearbox pump. What a joke.


As to what it does I have said my piece and FerrariFixer has said his and personally I do not want to stir this pot any more. Are you guys just trying to get me and Ferrarifixer to light off more fireworks?;-) I think that Ferrarifixer and I could certainly agree that in the big picturem the grub screw has a very minor roll. The car will run fine without that nut. If I took it out of your car you would never know it. Ultimately we both treat it the same way as it goes in after the big nut where the effect of such has questionable merit. I have shown in pictures above you can alter flywheel position with this small nut and those on this board can use that information as they see fit. Ferrari in the WSM is completely silent on this issue and there is no TSB that I know of that disscusses this topic.

As to your tool it looks good from here but can it take the abuse of an impact gun? Baum makes its tools this way and they break. Do you heat treat your tools? My hillbilly heat treat of my home made mild steel tool works and looks better than Baum's. I just used kasdenit heat and motor oil and my tool is still going strong. I just used it yesterday to post my ictures in this thread.

 

I get all my ring nut tools made in exactly the same way as that shown ( I thought it was my idea as I'd not seen it before I did it!!) I have made all I need for 246/308/BB/328/348/355/360.....engines and gearboxes and clutches and wheel brgs.

FBB, I concede that the flywheel position can be moved a bit... but I don't see how this will effect the clutch adjustment. The throw out brg will sit on the tip of the clutch fingers no matter where that is.... they self adjust.

Also, I feel that if the flywheel spigot is not fully inside the brg with the big nut fully tightened, it will promote brg wear/vibration.

 

I still think that we need to clarify things on this thread though? (For future reference as its very unclear!) The torque of the flywheel bolt would be handy - I can not actualy find it in my WSM? (Anyone - Please ?)

M12 grade 12.9 has a recomended max tightening torque of 105 lbft and when you consider that in other situations a lock nut or half nut only has half the thread engagement and it never gets the same amount of torque as the full nut yet it still manages to keep it locked up? Food for thought?

I am only trying to get to the bottom of this so dont shoot the messenger

Paul

 

I'll take a shot at the summary (I don't mind being the messenger who gets shot).

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).

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.

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).

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).

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.