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360 Clutch slip / rev flare on downshift, quirky fault

Discussion in '360/430' started by wbt, Mar 31, 2019.

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  1. wbt

    wbt Karting

    Nov 28, 2014
    234
    New Zealand
    Full Name:
    Wayne
    #1 wbt, Mar 31, 2019
    I have an interesting situation with my car. Some time ago I purchased a full clutch kit for my tech to install (experienced guys, know the cars, well respected locally). And by clutch kit I mean everything, flywheel, clutch, pressure plate, bearing, flange, ring gear, position sensor, magnet and every seal, nut, bolt and screw inside the housing. All factory parts.

    As I had very recently purchased the car I can't be 100% sure, but I'm reasonably confident the fault wasn't happening before the clutch change (the old clutch was completely worn though on removal and gave 30,000+ km's lifetime). Car is a 2000 360 with CS TCU upgrade.

    Anyway, this is the symptom:

    On lighter throttle conditions downshifts result in a noticeable "slip" for 1-2 seconds before the clutch completely closes. For example highway cruising in 5th and change down to 4th to overtake result in a nice crisp clutch open and rev match from the engine, however the power returns before the clutch closes resulting in a significant over-rev before closing home.

    The problem does not occur at higher revs or with a mashed throttle, where downshifts are then very rapid and clean with no problems. Changing in or out of sport mode makes no difference. Very occasionally there is also a small rev flare on upshift. There are no warning lights, no stored codes and clutch PIS setup appears to be good with nice feeling pick up off the line. F1 pressure seems good and primes 5-10 seconds every few minutes. Factory scanners have been plugged in and everything including PIS setup double checked.

    My thinking is there is a clutch position sensor issue giving spurious readings within the TCU margin of error. My tech suggests a sticky throw out bearing, however the TCU should be smart enough to know if the clutch is not yet closed and hold back the engine throttle return, correct? I suspect the position sensor as the new sensor came with a magnet, but I have since read this magnet should be discarded and the old one re-used. Does anyone have experience with a new magnet or reversed magnet installation and how it would become visible?

    My tech is supportive and we will work together to fix the problem, so no issues there, however before committing to pulling the whole transmission out again I would like to know if anyone has experienced this before and what the cause was? Ideally first hand experience with similar symptoms rather than speculation.
     
  2. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,650
    China and California
    #2 24000rpm, Mar 31, 2019
    ok, you got me. I had the same problem.

    back ground of me: I am an 'experimentation guy. By that i mean i usually do something others wont' recommend me to do , just to see what would happen.
    For example, I tried to use a maserati clutch on a 430 and it failed me miserably. People would say " hey, u want to save money, that's what you get". But they really don't get it. Experimentation is part of the fun.

    To the point:

    I had the exact problem as you do. i replaced a worn-out clutch wihtout replacing the pressure plate. so it slips and I was thinking it is the pressure plate not good no more. then I remove the gearbox again and replaced a new pressure plate. Guess what, it still slips. please note that NOTHING was changed in the process except the clutch and the pressure plate. Not even the throw out bearing (which is leaking badly). I don't want to replace a leaking throw out bearing because i don't want other variables to complicate issues.

    so then the 3rd time, i replaced the throw out bearing. Still, clutch slips.

    i think your clutch psotion sensor theory is correct if the TCU isn't that smart. But do we know if the TCU is that smart? I don't. hope somebody else chimes in.
    Otherwise, i'd think it is a throw out bearing and its flange's 'bed-in' problem. just a theory.

    edit: i don't quite understand your "magnet theory" although i may have some feel for it, maybe because of my english as a 2nd language. could you use plain english to elaborate more on that?
     
  3. 24000rpm

    24000rpm F1 Rookie

    Aug 31, 2012
    4,650
    China and California
    #3 24000rpm, Mar 31, 2019
    long time ago I heard a "clutch position sensor reset" . not sure what it is , must be some trick there?

    something along the procedure that we didn't do to have caused this? maybe?
     
  4. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
    2,343
    Frederick, Maryland
    Full Name:
    Brian Brown
    #4 Motob, Apr 1, 2019
    The new magnet should be fine. Usually magnets lose magnetism with age. I replace the magnet when I install a new sensor. The magnet is installed in a holder, held in by a cap screw. It doesn't matter which way the magnet is positioned in the holder (there are no markings on the magnet to indicate north or south poles), So I don't think that the magnet in the holder orientation is important. I hold the magnets next to the side of my toolbox, and the new magnets generally feel stronger that the old ones.

    The magnet holder is a square block with a post that is held into the throw-out bearing with a 2mm diameter roll pin. The position of the magnet inside the holder is asymmetrical (the distance from the mounting post to the center of the magnet is different from the from to the back). It is critical that the magnet holder is installed correctly in the throw-out bearing. It is different on different models of Ferrari, on a 360 the open end of the holder with the screw in cap must face the transaxle. It is the opposite on an f430 ( where the open end of the holder faces the engine). You can go to the factory parts catalogues on Ricambi America website and look under "clutch and controls-valid for F1-" to see the orientation of the magnet holder.

    If it is installed backwards, all of the clutch position settings will be incorrect. I have seen cars with backwards magnets made to work by making major changes to the closed clutch position figures, but it never seems to work quite right.

    After the new clutch was installed, there is a procedure that must be followed in order to bed the new clutch in, and make sure that the TCU knows that the clutch was replaced (clutch bleed, setting new closed clutch position, resetting wear index, kiss point (PIS) calibration).

    Before removing your transmission, it would be good to know what all of the clutch position measurements are, what the wear index is and what the clutch wear is. If everything looks good, then you may have a malfunctioning part (bad pressure plate or sticking throw-out bearing) that no amount of reprogramming of TCU settings will compensate for. The TCU is not smart enough to compensate for a sticking throw-out bearing.
     
    WyattWhy, wbt and Flyingbrick242 like this.
  5. Mel Spillman

    Mel Spillman Formula Junior
    Silver Subscribed

    Nov 3, 2012
    706
    Sugar Land, Tx
    #5 Mel Spillman, Apr 1, 2019
    I had the same problem with my 360. We replaced the sensor with the New magnet and could never get the PSI correct. Finally, after six months of this BS, the new magnet was replaced with the original small magnet, and now everything works perfectly. Good luck with your problem and I hope this helps, Mel
     
  6. Flyingbrick242

    Flyingbrick242 Formula Junior
    Silver Subscribed

    Feb 26, 2017
    657
    Northern AZ.
    #6 Flyingbrick242, Apr 1, 2019

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