Symptoms of clutch slip on Fiat comfortmatic

Discussion in 'Fiat' started by Serendipitous, May 6, 2014.

  1. Serendipitous

    Serendipitous Funster

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    Hi. Got an odd symptom with my Fiat 3.0L comfort matic gearbox/clutch. I've had a couple of occurrences at around 2000 rpm in 6th where when accelerating relatively gently the revs rise as if the clutch is slipping. Easing off stops it.

    Accelerating again doesn't produce the same result.

    Engine pulls well under high load on hills etc without any symptoms of clutch slip.

    Any thoughts?
     
  2. Zajacp

    Zajacp Funster

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    Just had same problems with mine but it's got a fully manual clutch system
    Turned out to be the dual mass fly wheel.
     
  3. RS_rob

    RS_rob Funster

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    DMF - Duel Mass Flywheel.

    They are fitted to all modern motors & cannot cope with high power in low gears, they r stupid things that fail earlier than a normal clutch would.

    What most likely has happened is youve applied too much power in to high a gear & because the dmf is supposed to eliminate vibration & move within itself it did & the result is actual clutch slip caused by the dmf.

    Don't wreck em they are expensive :Cool:
     
  4. old-mo

    old-mo Funster Extra Special Life Member

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    Is that using the fully auto mode or going through the gears manually.. ?

    When I first got mine.... Not being used to reversing it up a steep awkward drive and taking two bites at it... it would stink of burning clutch.. and flash up on the screen "Clutch Overheat"... :Sad:

    But as long as I go up in one motion It`s OK... which I do now with ease..:thumb:

    Just done a 4 thousand mile trip abroad with a 4 wheel trailer and car on.... no problems, all done in the auto mode..

    Had it serviced a couple of weeks ago and pointed out the clutch slip scenario.. and from a fully fledged "Fiat" recognised dealer he said =

    Those vehicles and engine are built for a van or pick-up up to a weight off 2 - 3 tons... NOT for trying to drag 4 -5 - 6 ton of M/home around.. :RollEyes::Doh::Blush:

    Why do they build them as M/homes and sell them if they are not fit for the purpose..... I dont know says he.... :Angry::Blush::Blush:
     
  5. TheCaller

    TheCaller Funster

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    I'm sure we were all taught not to let engines labour in a high gear, but to change down (or not change up too soon if going up through the gears).

    Then fuel economy got more important, so we were all told to get into as high a gear as possible, as soon as possible.

    Diesels are relatively good at giving relatively high torque at low revs & soon run out of puff at high revs, so changing up early was no hardship. I stress the 'relatively' bit because the differences between modern petrol & diesel engines is a lot less than it was 20 years ago in that respect.

    Then along came Dual Mass Flywheels, in an attempt to reduce the vibration inherent in diesel engines. Apparently, DMFs really do not like high torque at low revs - in any gear. So we are back to the original advice - never let a DMF equipped diesel have full throttle at low revs & always reach a reasonable speed in each gear before changing up. I notice that my Comfortmatic has a higher change up point than I would use manually when in pootleing about driving mode.

    I long since lost track of modern diesel fuelling systems & the detail of how they work, but very few throttle pedals are directly connected to the fuel flow these days - there will be an engine management system in between.

    I'm told that city taxi drivers are death the DMFs. They sit in traffic jams & when it trickles forwards, they just lift their foot off the clutch & let the engine recover to tickover speed without touching the throttle. Of course, as the engine speed starts to drop, the engine management system tries to keep the revs where they are supposed to be & boots in a slug of fuel, even though the throttle pedal hasn't been touched. Cue knackered DMF. It's better to raise the revs a bit first, then feed in the clutch. The clutch is designed for it, the DMF isn't (even if it should have been).

    Even if it wears the clutch, it's a cheaper item to replace, although given the labour to change either, there is a strong argument for changing both if one needs doing.

    That's the story as told to me. Others with recent training on modern diesel power trains may have a different take on it, or may be able to explain the reasoning more clearly.
     
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  6. Techno

    Techno Funster Life Member

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    The comfortmatic is great in most respects but it is not clever enough to read your mind.
    With a manual you would change down to 5th or 4th before booting it but in auto the computer only knows that you just put your foot down and goes WTF :Eeek: The power delivery in 6th is far more than the clutch can handle before the computer shifts gear for you.
    That's my take on it
    39k miles still rolling

    EDIT even mild acceleration in 6th can slip as its just too much for more than cruising. If you ever use the cruise control (I dont) you'll notice that even mild inclines result in the computer throwing it into 5th or 4th
     
    Last edited: May 6, 2014
  7. Serendipitous

    Serendipitous Funster

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    Thanks for the replies.:Smile:

    The gearbox is normally operated in full auto

    I guess the point is that I don't consider the drive train was under significant load when the slip symptoms occurred. No harsh acceleration or steep inclines etc.

    Could be best described as if you had rested a heavy foot on the clutch. Can't quite put my finger on the conditions before it occurs as it's very infrequent and always a surprise. :Eeek:
     
  8. Portland

    Portland Funster

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    I had the early version in a 2003 Hymer with a Sallyspeed gearbox with normal clutch. This had two ranges with a red button to change from economy / normal or winter/ summer settings. The winter setting reduced the gear changes and was good for motorway running but it allowed the clutch to slip at low speed or on hills and could make the clutch overheat ( as we discovered taking the rural route from Santander to Burgos). If yours has this device I would try the difference.
     
  9. RS_rob

    RS_rob Funster

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    My last van was a vw T4 modified I had doubled the power from 88bhp to 150bhp & pushed the torque up to 284.4nm
    When rolling road tested it was done in 4th & I asked why it is to do the the power delivery & how the gears are matched to the engine 4th is always a 1-1 ratio.

    Needless to say the DMF only lasted a week :Rofl1:
     
  10. pappajohn

    pappajohn Funster Life Member

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    i know why Mo.....because the auto function appeals to motorhome drivers and if thats what they want the converters will use them.
     
  11. TheDogMan

    TheDogMan Funster

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    They are just uprated vans and not matter how they uprate them they are still base vans with van running gear and should be driven and used with a degree of care, if you want a proper chassis built to carry the weights on some of these large ones it can only be a Merc or Iveco
     
  12. Geo

    Geo Trader - Funster

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    Wont help the OP but will show how they work and what they do
    The extra dampening is reqd because modern engines develop so much more tourque at lower revs that it is claimed that standard clutches would not be up to the job.
    I does however beg the question ? "Why do they make conversion kits" ie back to a standard set up and how do they manage to work:Doh:
    I personally think it is an experiment that all the designers took to cos it gave them something different to draw:RollEyes:

    [ame="https://www.youtube.com/watch?v=YnaXB8q3uzQ"]3D animation of dual mass flywheel - YouTube[/ame]
     
  13. makems

    makems Funster Life Member

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    Hmmmm.... our comfortmatic Cruise control NEVER changes down itself.
    Ours just gets slower and slower until the cruise control gives up and you return to having to use the right foot. After a while you just get used to having to use the accelerator pedal on hills and take your foot off again at the top when normal service resumes.
    Our previous Rapido was on a Merc with a "proper" auto box which did indeed change down on hills when required without any intervention.
    I thought the behaviour on our Comfortmatic was just the way it's supposed to be, not being a proper auto.
    Now you've got me wondering if there's a problem:Eeek:
     
  14. TheCaller

    TheCaller Funster

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    That sounds like a problem to me, but I can't think what would cause it.

    I normally only use the cruise control on motorways & the like, so a gear change wouldn't normally be called for, but I'm almost certain that mine changes gear just as it would if I was controlling the throttle myself.

    When you do intervene & press the throttle yourself, does it change down then? If not, it sounds as if the box has switched to manual.

    My understanding is that the cruise control operates on the throttle. The gearbox is supposed to react to speed & throttle setting, so it shouldn't make any difference whether the throttle is being set by you or by the cruise control.
     
  15. ivorantony

    ivorantony Funster

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    That's not how it should work I'm afraid, once on a incline with extra load the ECU will increase the throttle steadily until the vehicle speed remains steady at your preset limits or slightly below, if it cannot within the turbo boost/ min revs
    Parameters it should drop to a lower gear,
    I use a mark one eyeball to look ahead :thumb: any hill that would cause a downshift on the box is taken care of by me, a quick flick into a lower gear is so much kinder to engine/ gearbox and clutch,
     
  16. makems

    makems Funster Life Member

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    Definitely a problem then.
    I'll get it looked at as it's still under warranty.
    And no it doesn't seems as if there is any kick down either whci a normal auto box has.
    I can't tell properly as I don't drive the damn thing because of defective eyesight. Gwen is the pilot, I am just the observer. :Sad:
     
  17. Techno

    Techno Funster Life Member

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    Yes a problem for sure
    I deliberately don't use it because it over reacts like a tw@t :Laughing:
    I can get over most hills in 6th without dropping under 50mph. If I set cruise to 60 it would be in fourth before it dropped to 57 :Angry:
     
  18. TheCaller

    TheCaller Funster

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    Maybe they set it like that to protect the DMF from too much torque at low revs. :Laughing::Laughing:
    Isn't this where we came in? :Wink:
     
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  19. Serendipitous

    Serendipitous Funster

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    Well one thing is clear from the comments and replies, whilst the same (titled) box is fitted they seem to perform in different manners.

    I was very impressed with the box as it mimics very well what I'd expect to do with a manual. Particularly so the change down when breaking.

    There is no evidence of slip when accelerating or on hills. As said occurs around 2,000 rpm under lightish loads. In practice because it's noticeable (I find the slip on torque converters annoying) the revs only rise at most by couple of hundred.

    Plan to make carefully note of symptoms.

    As a thought any known issues with oil or filters etc.

    incidentally the box has only done 12,000 miles. Previous owner didn't go very far it seems.
     
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