Tell me what happened????

Discussion in 'U-shift em' started by Tim, Oct 12, 2010.

  1. Tim

    Tim Silver Level contributor

    I was driving my four speed the other day down an on ramp, and I was going about 10mph in first when I floored it, hit second at 5,300rpm and then went for third and the clutch pedal stuck to the floor and would not come up. It was like the car was in neutral, rev engine and still coasting. I thought I broke the Z bar or other linkage but everything is connected and moves. I can bring the clutch pedal up with my hand. I get it towed home and remove the inspection plate. I move the clutch linkage and I can see that the throwout bearing is moving back and forth on the input shaft and clutch fork. The clutch disk is not in contact with the flywheel it is a if someone is pushing the clutch pedal in???I have a Centerforce dual friction pressure plate and disk with 4,000 miles.

    Can anyone tell me what happened before I pull the tranny???
    Thanks
    Tim
     
  2. pphil

    pphil Well-Known Member

    now this is a mystery

    i have had the pressure plate collapse but it would still pull (still be engaged)
    with the petal out how could the clutch be disengaged
    i mean the throwout bearing is the only thing that could press against it.

    please let us know how this turns out

    scott
     
  3. cstanley-gs

    cstanley-gs Silver Mist

    ok someone school me...

    isnt the pressure always on the flywheel? And when you press the clutch, it pulls it away? so it sounds like something is preventing the the clutch from returning to the flywheel...


    I know its no help, but a learning opportunity for me :)
     
  4. CJay

    CJay Supercar owner Staff Member

    Im not sure why the clutch pedal wouldnt come back up to the top. Do you not run a clutch pedal return spring?

    Almost sounds like the diaphram springs on the pressure plate bent or popped the opposite way if that possible. But it sounds like you have a bad pressure plate.
     
  5. Tim

    Tim Silver Level contributor

    I do have a light return spring on the pedal so it does come back up half way .
    :3gears:
     
  6. David Hemker

    David Hemker Well-Known Member

    The pedal return spring should have nothing to do with this as it's only purpose is to pull the throwout bearing away from the fingers so it does not prematurely wear out. This is why there is free play in the pedal/linkage.

    It sounds like the pressure plate malfunctioned. I have heard of this but never had it happen to me. Either the clamping/pressure springs went bad and will not engage, the leverage mechanism between the fingers and springs broke or locked or the diaphram finger springs gave way.
     
  7. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    That's odd. The Centerforce dual friction clutches had weights on the diaphram fingers so the higher the rpm, the higher the clamping force. How far can you move the throwout bearing before it contacts the pressure plate? Or rather, do you have full travel of the pedal before it contacts the pressure plate? I've never heard of one of these going over-center but I suppose anything is possible.
     
  8. Briz

    Briz Founders Club Member

    Had the same thing happen on a tractor.(1950 Furguson) Once I seperated the bellhousing from the motor I found all the fingers stuck in so the plate was pulled away from the disk. As soon as I losened the first mounting bolt the plate snaped back against the disk. I dont know what caused it to do that. I replaced it due to it being such a pain to get to. Never had another problem.
     
  9. Tim

    Tim Silver Level contributor

    I do have full pedal travel but it seems like it never hits the fingers on the pressure plate. I am assuming that the fingers are stuck pushed in rather than out. If this is what happened, then why did it happen? Is my clutch linkage too long and it pushed the fingers in too far, is this even possible? I will tear into it this Friday. I wonder if it would return if I loosened a few pressure plate bolts??? I
     
  10. Golden Oldie 65

    Golden Oldie 65 Well-Known Member

    Same thing I was wondering. Before I pulled the transmission I would see if I could get a pry bar in there and try to release it, or if you have to, loosen the bolts like you mentioned. If that works then perhaps you could re-adjust the clutch linkage so it wouldn't push it in so far in. Worth a try.
     
  11. Jclstrike

    Jclstrike Well-Known Member

    Not to hijack this and I have no clue why myself..but wondering what the springs are being mentioned? I know my car has no springs on anything at all since Ive owned it.
     
  12. CJay

    CJay Supercar owner Staff Member


    The clutch fork should have a spring on it that goes to a hole in the frame. It keeps the bearing from riding on the pressure plate. Here's a pic-
     

    Attached Files:

  13. Jclstrike

    Jclstrike Well-Known Member

    Thanks I will have to find one for my car.
     
  14. BadBrad

    BadBrad Got 4-speed?

    Probably have a broken piece of something jammed there preventing the diaphram from returning to resting position. Very odd, yet I've had stuff break inside the bellhousing and get tossed about making a hella racket until stuff finds a new home. Have also removed pressure plates and found stuff in there that was not exactly as the factory intended. Most likely you broke something and jammed up the mechanism; it doesn't take much. Have you always had smooth clutch action; never a sticky pedal or rotational noise?

    As mentioned earlier a collapsed pressure plate will fail to disengage the driven disc (not your problem); you'll be unable to stop the vehicle without forcing it out of gear or shutting off the engine. I nearly had a car go through a store front for this reason. That's pretty much an "OH SH!T!" moment. Only fast thinking prevents disaster.
     
  15. staged70

    staged70 RIP

    Most likely culprit is the pressure plate. You will be pulling the trans. Let us know what you find with pics
     
  16. snowman4839

    snowman4839 69 Turbo Buick

    If you still feel the pressure against your foot when you press in the clutch pedal, then that's just weird and I'm not sure.

    But if you don't feel pressure (or hardly any because of the clutch return spring), the fingers of the pressure plate are stuck in and are not applying any pressure to the clutch disc and therefore the rest of the your powertrain.

    All signs point to your pressure plate being defective for some reason or another.


    For the person asking about the spring, the spring pulls the throw-out bearing off of the pressure plate fingers. This prevents premature wear. The first part of when you press in the clutch petal and you hardly feel any resistance, that's the throw-out bearing return spring.
    Then when you get to the hard part and you actually have to apply a good bit of pressure on the clutch pedal, then your throw-out bearing has made contact with the pressure plate fingers and as you push through, it is releasing the pressure that the pressure plate has on the clutch disc. The clutch disk is the only thing connected to the transmission. The pressure plate is bolted directly to the flywheel.

    Sorry if that was a useless and lengthy explanation but I spent a few weeks trying to understand how all that fit together and I finally just got under my car and replaced the clutch/pressure plate/throw-out bearing over a few days after school and that made everything a lot clearer.
     
  17. wkillgs

    wkillgs Gold Level Contributor

    Give Centerforce a call and speak to someone in Tech Support. Maybe they've seen the problem before.
     
  18. Tim

    Tim Silver Level contributor

    I did call Centerforce and the tech thinks that something broke and has jammed the pressure plate. He is also very curious on what happened and wants me to call him back when I find out. I am hoping that if it is a defective pressure plate that they will warranty it.:TU:
     
  19. speedtigger

    speedtigger 9 Second Club

    Back in the day when I was a gear jammer the diaphragm style pressure plates would stick to the floor at high RPM (typically above 6k). We always used the 3 finger clutches for that reason. Then they started adding weights to the diaphragm style clutches for better high RPM performance. However, once the RPM dropped low enough on the diaphragm style units, the clutch would re-engage. Had me scratching my head the first time it happened.
     
  20. Tim

    Tim Silver Level contributor

    Ok I pulled my trans and wouldn't you know it, I hear a faint pop and the pressure plate engaged. So now the disk is touching the fly wheel. I took pictures of the pressure plate. Does anyone see if there is something wrong?? I feel like putting it back together and adjusting the clutch pedal so it doesn't have so much travel.
    ????
     

    Attached Files:

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