348 - Squealing sound goes away with light clutch pressure? | FerrariChat

348 Squealing sound goes away with light clutch pressure?

Discussion in '348/355' started by jlclt348, Apr 28, 2020.

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  1. jlclt348

    jlclt348 Karting

    Jul 7, 2013
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    Justin
    Gents - I have an intermittent issue with my 348 spider. It's an annoying squealing sound from the back. It goes away if I lightly push on the clutch pedal. No more than a 1mm of pressure and the sound goes away. The sound will go away after a few cycles of clutch pressure, then it will come back 20-30 min later. This happens regardless if the car is in gear or neutral. The obvious thing is it's clutch related. The clutch does engage at the top of pedal. Is it adjustable? Am I slowly shredding something important?
     
  2. yelcab

    yelcab F1 World Champ
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    Hydraulic clutch on the 348 is not adjustable. Engagement at the top of the travel and squealing sound mean you are due for a slave bearing. The original Ferrari bearing is of poor design for this environment and will leave you stranded very soon. The better replacement is Hill Engineering bearing. Get it from Ricambi, @Ricambi America.
     
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  3. m.stojanovic

    m.stojanovic F1 Rookie
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    I have joined Justin's club - "squealing clutch slave bearing".

    Recently, I replaced my original (leaking) slave bearing with one from Hill Engineering. I replaced only the slave/bearing unit and kept the original flange as it was still in very good condition. I noticed only one slight "mismatch" - the recesses for the preload springs are, on the Hill bearing, spaced slightly further apart in relation to the spacing of the recesses on the original flange (and the original bearing) so the springs are now sitting slightly angled. Not so much when the Hill bearing is extended (clutch disengaged) but more so when the bearing is in position of engaged clutch (clutch pedal released). When the pedal is released, the two springs create preload on the bearing to keep it in contact, and turning, with the clutch "fingers".

    So, I now have no more leaks of clutch fluid but I have a quite high pitch squealing sound from the pumpkin which stops with a very light pressure on the clutch pedal, i.e. with provision of very small additional preload on the bearing. It appears that now, since the preload springs are somewhat angled resulting in their reduced preloading force, the clutch "fingers" slip over the bearing "nose" producing the squealing sound. To make things worse, I kept the original (32 years old, probably tired) preloading springs instead of replacing them with new ones (silly me).

    The squealing will stop if I hold the pedal pressed for a couple of minutes and will not re-appear until the engine cools down. I am still trying to "run-in" the new bearing hoping it will stop squealing but it may not. I may have to replace the preloading springs or even the flange (with the Hill one, to eliminate the "angling" of the springs). My questions:

    1. Justin, did you solve your squealing? Did you have it, like me, after installing a new Hill bearing on original flange or did it just appear? How did you solve it?

    2. Has anyone installed a new Hill bearing keeping the original flange (causing angled springs)? If yes, did it result in any squealing? If no squealing, did you keep the original springs or installed new ones?

    I am trying to find out whether, perhaps, I can solve my squealing issue if I just replace the preloading springs with new ones. Has anyone compared the lengths of old and new springs?
     
  4. Ferrarium

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    #4 Ferrarium, Aug 18, 2023
    Last edited: Aug 18, 2023
    Not saying its the issue but worth mentioning is all, there were 2 different flanges for the 348, the Hill TB is designed to work with flanges #168589 & #158209. Early flanges have a dimension of 82mm while the later flange as shown has 86mm. The Hill TB was designed for the 86mm spacing flange.

    The dimension is the the spring hole centers.
     

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  5. yelcab

    yelcab F1 World Champ
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    I have used the HE bearing on stock flanges on 355 with no issues, but I have not done it on a 348.
     
  6. Ferrarium

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    Yes, the 355's all had the 86mm flange. I have a spare OEM flange if it is 86mm and that is the issue I can send it to you. When I did mine I did not even bother checking I just replaced it.
     
  7. m.stojanovic

    m.stojanovic F1 Rookie
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    Thanks for the good info. I have done a check and found the following (using the spring spacing info provided by Eric):

    Flanges:
    138378 --- 348 early (probably 82 mm spring spacing)
    144984 --- (82 mm spring spacing) 348 later & 355 2.7 till gearbox No. 2438
    168589 --- (86 mm spring spacing) 355 5.2 from gearbox No. 2439 and till No. 2715
    158209 --- (86 mm spring spacing) 355 5.2 from transmission No. 2716 on

    According to the parts diagrams, it seems that flanges with wider (86 mm) spring spacing were not used on 348s but only on 5.2 355s. It means that I would need to get a flange for 5.2 355 (168589 or 158209), or one from Hill, in order to match the spacings of the spring recesses with the Hill's slave/bearing.

    Does the 355 5.2 flange fit the 348? I guess it does if the Hill's flange (86 mm spring spacing) fits both, 348 & 355.

    It can be seen on the pics below that the spacing of the spring recesses is indeed wider on the later 355 flange.

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    Eric, have you checked the spacing of the spring recesses on your original flange? (it should be 82 mm since all 348s use flange 144984)
     
  8. Ferrarium

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    I just went to check but I can't find my flange it might have gotten chucked with rotors and a bunch of stuff. It was an October 90 build so I assumed it was 82mm and just bought the hill flange.
     
  9. m.stojanovic

    m.stojanovic F1 Rookie
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    I have been testing the squealing from my release bearing daily for about a week and the time for it to stop has now reduced from ~2 min to less than 1 min but I don't believe it will completely stop. I have therefore decided to open-up the pumpkin again and install new preloading springs. In addition, since my 82 mm flange is very good, I am thinking of "dremelling" (making oval) the spring recesses by 2 mm out to get 86 mm and have the springs sitting straight/parallel. I see no reason why I should not go for this solution.

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  10. Ferrarium

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    Worth a try since your doing the work not paying someone. Maybe use a plunging end mill correct size on a drill press though and only go down so deep. Much better than free handing a Dremel. Not sure what stops the springs from shifting back though.
     
  11. m.stojanovic

    m.stojanovic F1 Rookie
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    The springs cannot shift back to 82 mm spacing at the flange because the wider (86 mm) spacing on the slave cylinder is, as I observed when bench/hand testing, actually "trying" to pull them further apart. In addition, during my testing I noticed that, when I compressed the springs to the position as when the clutch pedal is released, the body of the Hill slave was coming into light contact with the springs near the flange and this was also "trying" to spread the springs further out from their 82 mm spacing. When the springs are straight/parallel they will be in a more stable position and will tend to stay there, i.e. will not have any tendency to slide inwards at their ends at the flange.
     
  12. Ferrarium

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    Right makes sense I can see it in my head now.
     
  13. ernie

    ernie Two Time F1 World Champ
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    Remember,

    There is also a bearing on the clutch bell housing/ aka pumpkin. It sits behind the bearing cover, with the cavallino stamped on it. You may want to have a look at that just to make sure it isn’t also failing/squealing.
     
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  14. 308 GTB

    308 GTB F1 World Champ
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    Right, Ernie. They rarely fail but when they do...


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    It happened to me at Watkins Glen. All the balls were out of the cage. What a racket that made!
     
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  15. m.stojanovic

    m.stojanovic F1 Rookie
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    I am convinced that, in my case, the squealing is caused by insufficient preload on the release bearing, for the reasons I described earlier, causing the clutch fingers to slip over the bearing race and "sing" (like tuning forks). The sound is a continuous high pitch (frequency) tone which stops with just a very light pressure on the clutch pedal. I didn't have this sound before and all I did was replace the slave/bearing unit.
     
  16. Ferrarium

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    I replaced my spring when I did mine but did not notice any tension difference using my fingers btw. It was not like the old springs were shot or anything. Could be that angle.
     
  17. m.stojanovic

    m.stojanovic F1 Rookie
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    I have removed my slave/release bearing and compared the old and new springs.

    Free length: Old 55.6 mm; New 56.5 mm. Then I compared the spring lengths when compressed:

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    So, the old springs are indeed a bit "tired". Not that much but, considering how little pressure I had to apply to the clutch pedal to stop the squeal, the extra spring rate of the new springs would probably eliminate the squeal even if angled (due to different spacings of the spring pockets). With the modification that I am going to do on the spring pockets on the flange to increase their spacing to 86 mm to keep the springs straight/parallel, which will further increase the spring force on the bearing, I am confident that there will be no more squeals.

    Eric, did you maybe check the stiffness/tightness of the Hill release bearing? On my Hill bearing, when I place it flat on the bench with the inner race up and try to rotate it by placing one finger of each hand at opposite points, I have to press my fingers quite a bit to be able to turn it. As I turn it, it feels very smooth but with some "viscous" resistance. This is now after more than one hour total time of "running-in" the bearing. I guess it will loosen up a bit after a longer run.
     
  18. Ferrarium

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    I recall maybe I did and it seemed normal perhaps a bit tight compared to OEM one and forgot about it, nothing stuck in my mind about it except it felt different than the OEM one.
     
  19. Ricambi America

    Ricambi America F1 World Champ
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    100% normal.
     
  20. m.stojanovic

    m.stojanovic F1 Rookie
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    I decided to have the spring pockets modified by a professional machining shop (and it cost just $12). I will probably complete the re-installation in a couple of days and report on the results.

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  21. Ferrarium

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    Yes excellent.
     
  22. m.stojanovic

    m.stojanovic F1 Rookie
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  23. m.stojanovic

    m.stojanovic F1 Rookie
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    Squealing release bearing update: I just completed re-installation of the release bearing with now 86 mm spring spacing on the flange and with new springs (which showed somewhat higher rate than the old ones). In addition, as an "insurance", I inserted 1.2 mm thick washers as spacers inside the spring pockets on the slave cylinder just to create a bit higher preload than standard in view of my HE bearing being fairly stiff, as I determined when trying to turn it by hand.

    However, I still have the squealing on cold engine start-up. There is some improvement though - before, the squealing would stop with very light pressure on the clutch pedal; now it will stop with very very light pressure, with just a "touch" I would describe it. Still, it took ~1.5 min of keeping some pressure on the clutch pedal (and forcing the bearing to rotate together with the clutch fingers) before the squeal would not return after releasing the pedal. Since the setup of the springs on my slave cylinder is now as it should be, and since I have new springs and even created a bit higher force from them by inserting washers (spacers), I had to conclude that my HE bearing must be a bit too stiff causing the clutch fingers to slip over it.

    I bought the HE slave/bearing in 2016 and kept it as spare (air-conditioned room) until now. Maybe its extra stiffness has something to do with the long storage? I have written to Hill Engineering asking for their advice as to whether I should get a new one (although the bearing should not have a "shelf life"). In the meantime, I will continue trying to "run-in" the bearing over the next week or so hoping that it will eventually stop slipping and squealing as it seems that it is now "almost there".
     
  24. m.stojanovic

    m.stojanovic F1 Rookie
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    Squealing release bearing update: I have received response from Hill who, based on my description what force of my two fingers I had to apply to the bearing's inner race to turn it, concluded that my bearing is considerably stiffer than what it should be. It seems that this was caused by my keeping the bearing for 7 years before installation which possibly caused some thickening of the bearing grease causing increased drag.

    Hill also believes that, given more time and RPM, the bearing (and grease) should loosen up and stop slipping/squealing. Well, I have been, so far, rather gentle with the bearing running it only at up to 2,000 rpm at home (and neighbours). I will now drive the car out and let the bearing see some 7,000 RPM so it will either loosen-up or blow-up (will see).
     
  25. Ferrarium

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    Interesting, 7 years is a long time, but I recall by bearing was quite stiff to rotate as well.
    Maybe an extended drive with all temps at full time for an hour or so. Long highway run perhaps.
     

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