348 Clutch Options

I searched and didn't find any recent threads about this. My 348 has the AP twin disc setup, which unfortunately got soaked with trans fluid and Kluber grease when my triple seals failed. In addition one of the diaphragm spring fingers broke off at some point in the past. I need a new clutch. In surveying my options, this is what I've found so far:

-Replace with the same AP twin disc (~$2200 plus the cost to reface the flywheel)
-Reface my clutch (~$500) but then I have to find a new diaphragm spring (no idea where to get that)
-Change to a single disc clutch (~$1300 plus the cost of the correct flywheel $$$$)
-Upgrade to something else (MD Clutches makes several options)

What have people tried and what has been successful/not successful? I have reached out to MD about their single mass flywheel conversion for the F355. They said that there is no equivalent 348 kit available. They suggested a ceramic 348 clutch, but warned that flywheel wear would be accelerated. With these flywheels being evidently expensive and hard to source I am not sure I want a clutch that will wear it out faster. They also offer a Kevlar clutch but I'd like to hear some independent reviews from people that converted to it. Overall I am trying to find a reasonable cost reliable clutch setup for my car. I autocross it and will be doing track days in the future, but I also do a lot of street driving. My concern is that a spontaneous triple seal leak can trash a $2200 clutch, and the stock clutch apparently has a problem with the diaphragm spring fingers breaking off (I've read of others that experienced this). I should also point out that I didn't have any real problems with the stock clutch until now. I think the pedal feel is fine and the balky shifting is more due to the transmission in these cars than the clutch (though the broken spring finger likely was a contributing factor).

Image Unavailable, Please Login

Image Unavailable, Please Login
Image Unavailable, Please Login

 

Are you saying that the flywheel etc are not machined flat? Who would be able to remachine these parts correctly?

 

I read Ernie's entire write-up that you linked. Very well done. However, the MD Clutches website does not seem to indicate that a dish is needed as your diagram explains. They say that the factory flywheel has an almost imperceptible dish, which sounds like less than the 0.5 mm your diagram shows. What is the original source of your diagram?

http://www.inspiredservices.org.uk/mdclutches/dppfly.html
"You may hear some people mention the flywheel comes dished from new to help ease the drive take up. This is true, but only to a very small extent, when we have looked at new ones there is just the smallest of gaps, nothing that you would notice unless closely examined."

See #6 "Flywheel"
http://www.inspiredservices.org.uk/mdclutches/workguide.html
"Flywheel should be near as damit [sic] flat. It comes with a very slight dish, but you can hardly see this. If it has been cooked it warps and becomes very dished. This results in excessive wear on plate on outside and clutch slipping a lot easier as only small part of it is gripping, although you wont notice too much in everyday use"

 

Ok here's a complete update on what I ended up doing, and what I think of it:

I took the car apart in the fall. Everything was soaked in black sludge, a mixture of trans fluid, road grime, and Kluber grease from the flywheel torsion damper.

Image Unavailable, Please Login
Image Unavailable, Please Login

Image Unavailable, Please Login

The clutch had a broken diaphragm spring finger and has grease on it. I spent quite a bit of time cleaning everything up. Unfortunately I discovered that some idiot at the Ferrari dealer had wrecked my Voith damper on a previous clutch job. They must have machined the flywheel down but not shortened the pressure plate bolts. This meant that the bolts jutted out past the flywheel friction surface and pushed into the Voith damper cover, cracking it pretty badly and bending it as well. This **** is why I don't trust anybody, because at the end of the day their goal is to make money as quickly as possible, not to do a perfect job on your car.

Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
I spent a bit trying to survey my options, and ended up giving MD Clutches a call. Andrew was EXTREMELY helpful through this whole process, and I am grateful for the time he took to answer all of my emails. He was able to sell me a new Voith cover, as he had a single spare. From there, he convinced me to go with a ceramic single disc clutch. The reason is that the triple seals will likely leak again. If grease gets on an organic or Kevlar clutch face, you have to replace it. If it gets on a ceramic face, you can wipe it off with Acetone and reuse it. The single disc setup I bought comes with a new billet Steel flywheel, a new ceramic friction plate, and what appears to be a stock Valeo single disc pressure plate.

Image Unavailable, Please Login
Image Unavailable, Please Login

Image Unavailable, Please Login

Image Unavailable, Please Login

 

Image Unavailable, Please Login

Switching from the stock dual disc AP Racing clutch to the single disc ceramic was the first of 3 changes I made to the car. The second change was the triple seals. I ended up taking a hybrid approach on these. For the 2 seals closest to transmission fluid, I used the stock greenish grey hard plastic type. For the rear most seal, I used a new Viton one. My thought is that the the hard plastic ones will act as a sort of "baffle" or labyrinth seal to keep most of the splashing trans fluid at bay. The small amount that dribbles past them can be handled by the new, tight fitting Viton seal. I also like this because if the Viton seal fails, pieces of it can't migrate forward into the transmission because the hard plastic seals are in the way. If I used 3 Viton seals and the forward-most one fails, bits of it could end up in the transmission. Since the Viton is not OEM I'd rather not risk it until more people have put miles on them and know they don't ever tear apart.

Image Unavailable, Please Login

The third change I made was the trans fluid. Mine hadn't been changed since at least 2011, so I drained it. The color suggests that it was a conventional trans fluid, not a fancy synthetic one. I did quite a bit of reading and decided to try the Motul Gear 300 LS fluid.

Image Unavailable, Please Login

Image Unavailable, Please Login

I've now put about 250 miles on the car and can give my impressions. For change #1 (the clutch), I was amazed how light the pedal pressure is. It's honestly lighter than my Focus ST, which is a massive change from the stock dual disc. The release point is very near the top of the pedal travel as well, which took some getting used to at first. The first few miles did have some clutch chatter, but I think a combination of break-in and experience means that I can now easily slip leaving stop signs with no chatter. It bites really hard when driving aggressive, and I am not at all worried about clutch slip, even at the drag strip. Overall I like it. The only slight bummer is that I weighed the pressure plate + friction disc combo and it ended up being about 0.4 lb heavier than my old dual disc clutch. I'll bet the flywheel weighs more too, and I think the weight distribution definitely means it has a higher polar moment of inertia about the rotational axis. That being said, I can't really tell a difference while driving, so the difference isn't too much in the real world sense. Change #2 (the hybrid triple seal setup I tried) I can't really comment on. Time will tell if it is more resistant to leaks. Change #3 (the Motul trans fluid) did improve both cold and hot shifting. I no longer grind 3rd gear on fast upshifts. Cold shifting is improved as well. The only odd thing is that, for the improvement in upshifting I noticed, downshifting got worse. It's definitely less smooth and harder to downshift now than before. It's not completely unreasonable, but I definitely think that it's less enjoyable than it was. When I am driving really aggressive it doesn't really matter, as I can still downshift very quickly, it just takes more effort and feels less fluid to me. I haven't used other transmission fluids so I can't really compare to them. I just think the Motul overall was an improvement, and I will not be returning to conventional trans fluid in the future. Long story short I am satisfied with everything right now. I think in the future I want to design and build a custom torsion damper/flywheel/clutch setup and I still think there's a lot of room for improvement in this system, but for now this setup works well and takes abuse.