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Hydraulic Clutches

Discussion in 'The Hokey Ass Message Board' started by Root66, Aug 28, 2013.

  1. Root66
    Joined: Oct 6, 2008
    Posts: 85

    Root66
    Member
    from Norcal

    Am I correct in assuming that hydraulic clutch setups allow the throwout bearing to ride on the clutch fingers even when the clutch is engaged?

    With mechanical linkage we were always told to have some pedal free play to prevent contact with the TO bearing when the clutch is engaged and prevent premature failure of the TO bearing....have the rules changed for hydraulic setups? Is the TO bearing used with hydraulic setups different than mechanical linkage?
     
  2. Cyclone
    Joined: Mar 31, 2006
    Posts: 219

    Cyclone
    Member
    from Sonoma, CA

    I'm using a Ram hydraulic throw out bearing. When you set it up there is clearance between the fingers & bearing when its disengaged, so its just floating on the front bearing retainer, until you push the pedal.
     
    Last edited: Aug 28, 2013
  3. You could have a slave cylinder and fork mounted conventional TO bearing or an actual hydraulic throw out bearing.
    There's a spec clearance between fingers and bearing.
     
  4. Deuce Daddy Don
    Joined: Apr 27, 2008
    Posts: 4,959

    Deuce Daddy Don
    ALLIANCE MEMBER

    Never had a problem with my 1961 Ford Econoline set up using all stock componants.
     

  5. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,210

    Jmountainjr
    ALLIANCE MEMBER

    The spec for the amount of required clearance is different, but there is still clearance between the throw out bearing and the clutch fingers with a hydraulic TO bearing.
     
  6. Root66
    Joined: Oct 6, 2008
    Posts: 85

    Root66
    Member
    from Norcal

    With a master cylinder, a conventional slave cylinder and a sliding TO bearing the only thing that returns the pedal is the pressure plate pushing on the TO bearing and that pushes the fluid back up to the master cylinder....what causes any clearance between the TO bearing and the pressure plate?
     
  7. kursplat
    Joined: Apr 22, 2013
    Posts: 289

    kursplat
    ALLIANCE MEMBER

    light return spring on the clutch fork
     
  8. A return spring working against the slave cylinder to "return" it and the clutch fork to its set position. The exact same as a mechanical Z bar arraignment
     
  9. Phucker
    Joined: Sep 12, 2010
    Posts: 185

    Phucker
    Member
    from Kansas

    Depends on the type. I'm not sure if you may be looking to retrofit a newer transmission, but yes, on most newer factory stuff, the throwout bearing/slave combo, has constant contact.
     
    Last edited: Aug 28, 2013
  10. Root66
    Joined: Oct 6, 2008
    Posts: 85

    Root66
    Member
    from Norcal

    So the question remains, are the TO bearings used with factory hydraulic setups any different to allow them to spin continuously or were early predictions of doom overly pessimistic?
     
  11. With clutch fully engaged ( pedal up) there should be a speced clearance between the face of the TO bearing and the clutch fingers. 0.060 seems to be common.

    I have never seen nor heard anything remotely close to being any other way until your post. Curious as to how you reached your assumption?
     
  12. bobby_Socks
    Joined: Apr 12, 2006
    Posts: 938

    bobby_Socks
    Member
    from ǑǃƕǑ

    Do not know about factory setups but the ones that I have seen installed in a few hot rods did not spin continuously. Pretty good info hear. see attached file

    http://www.cjponyparts.com/images/art/install_HCC5.pdf
     

    Attached Files:

  13. Phucker
    Joined: Sep 12, 2010
    Posts: 185

    Phucker
    Member
    from Kansas

    There is NO clearance.....I repeat NO CLEARANCE. Depending on the style.

    You could be looking at better quality bearings, and or design/tolerances, designed for constant contact. Much like newer engines go for a lot more miles before rebuild. The life of a throwout bearing nowdays has a much longer expectancy.

    I feel a little offtopic going into this area, but to clear this up, here is a photo I hotlinked like an arsehole, from google images, of a new style throwout/slave combo. You will notice there is a spring behind the throwout bearing, coming from the face of the unit. That spring keeps the bearing constantly IN CONTACT WITH THE CLUTCH FINGERS. Its not a heavy spring, but yes, they do spin constantly. When you connect the transmission, it compresses that spring, and it stays compressed, untill the pedal is pushed. The position of the bearing in the picture is fully extended.

    [​IMG]
     
    Last edited: Aug 29, 2013
  14. bobby_Socks
    Joined: Apr 12, 2006
    Posts: 938

    bobby_Socks
    Member
    from ǑǃƕǑ



    ^^^^Learn something new everyday...^^^^
     
  15. ^^x2 never seen that before!
    Zero would be the speced clearance on that unit.

    Hey phucker how many and what manufactures use that?
    OEM or after market ?
     
  16. studebaker eric
    Joined: May 9, 2008
    Posts: 1,514

    studebaker eric
    Member
    from Diablo Ca.

    I had one that specified a .035 preload, but After about 500 miles, the clutch began to slip. Called the manufacturer and they said to pull the shims, so I got both answers on the same part.
     
  17. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,502

    greybeard360
    Member

    "riding the clutch" is what I always heard it called..... if you think about it for just a few minutes, you will figure out it is another old wives tale. I don't think the riding the clutch issue had anything to do with the throwout bearing. The belief was it was causing the clutch to slip and wear out. How far down do you have to push the pedal to get it to slip? Be a little uncomfortable driving with that much pressure on the pedal would't it?

    Think about how long wheel bearings last. They have pressure on them even sitting still. Differential bearings?

    The throwout bearing on MOST hydraulic clutches are in constant contact (never saw a factory one that wasn't) and that is the reason you NEVER have to adjust the clutch. Just like a 4 wheel disc brake car, the pedal remains the same no matter how thick (or thin) the pads are. 4 wheel drum car that retracts the shoes by springs.... remember the manual adjusted shoes? If they get out of adjustment (from wear) the pedal gets real low, adjust the brakes and the pedal comes back up. Why ? The pedal doesn't have to travel as far to expand the shoes.

    Ram has a bearing clearance? Finish the story..... they have that "hydraulic adjuster" in line to the slave to give you the "feel" of having a little free play. You have to keep adjusting it as the clutch wears.... just like a mechanical linkage. SO they aren't doing it to keep the bearing from wearing out.
     
    Last edited: Aug 29, 2013
  18. PackardV8
    Joined: Jun 7, 2007
    Posts: 889

    PackardV8
    Member

    Yes, difficult for we old guys to wrap our head around a throwout bearing which is pushing hard against the pressure plate all the time. That spring behind the pictured bearing is a stiff sucker.

    I used one in my Packard V8 in my Stude truck. So far, so good.

    jack vines
     
  19. Cyclone
    Joined: Mar 31, 2006
    Posts: 219

    Cyclone
    Member
    from Sonoma, CA

  20. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,502

    greybeard360
    Member

    That is only to set it up with the correct clearance so it won't over travel. It will be touching the bearing all the time once the clutch is bled and been pushed down 1 time.
     
  21. Root66
    Joined: Oct 6, 2008
    Posts: 85

    Root66
    Member
    from Norcal

    From the installation instructions for that product:
    "This hydraulic bearing is designed with a constant running bearing that will touch the fingers of the clutch at all times, but does not apply pressure when the clutch is engaged."
     
  22. Happydaze
    Joined: Aug 21, 2009
    Posts: 962

    Happydaze
    ALLIANCE MEMBER

    [​IMG]

    The manufacturers logo on that baby is AP for AP Racing, a UK manufacturer of racing and aftermarket upgrades, mainly brake and clutch stuff.

    Chris
     
  23. Kenneth S
    Joined: Dec 15, 2007
    Posts: 1,527

    Kenneth S
    Member

    I used that McLeod hyd t/o bearing setup, it worked great, and was trouble free.





    The OEM's (Ford, GM, Chrysler) have been using the same style of hyd t/o bearing as shown in the picture for many years now. Had to replace the one in my OT 97 Ford F150 at around 285,000 miles because the seal in it started seeping a little (I'm still running the original clutch, and pressure plate at close to 360,000 miles).
     
  24. ace high
    Joined: Dec 15, 2007
    Posts: 210

    ace high
    Member

    My McLoed Hydraulic T/O bearing is in constant contact with the pressure plate figures. The constant forward pressure caused the back end of the crankshaft to have forward pressure on it and caused the crank main bearing thrust surface to wear out. It took out all the crankshaft "end play".
     
  25. Boneyard51
    Joined: Dec 10, 2017
    Posts: 4,183

    Boneyard51
    Member

    The 60s model Ford pickups had clearance between the bearing and clutch forks. The hydraulic cyclinder travel never changed, you adjusted a rod just like mechanical linkage , to adjust the clutch. Bones
     
  26. Kenneth S
    Joined: Dec 15, 2007
    Posts: 1,527

    Kenneth S
    Member


    Only time I've seen that problem was with mechanical linkage with the proper free play in the pedal, cause was a bad oil filter (Fram).
     

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