How to tell when your clutch needs to be replaced.

Discussion in 'Trucks [ Eighteen Wheelers ]' started by BobbyTTour, Sep 4, 2012.

  1. bender

    bender Road Train Member

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    Just remember, when you turn that adjuster ring in or clockwise, it moves the release bearing back, closing the gap on the clutch brake and at the same time increasing the free travel clearance on the pedal. Turning the adjuster ring counter clockwise moves the release bearing forward toward the clutch, increases clutch brake air gap and lessens free travel on pedal.

    If you ever have frozen linkage adjustments etc and need to temporarily make due to get the job done, you can bend your style of lock to fit down into the adjuster and retain the adjustment.
     
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  3. 55_cans

    55_cans Light Load Member

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    :) lol, how did you know what I did?

    Wasn't my greatest moment, but I had 20 min to go/no go, and I didn't want to forfeit the work as hauling was part of it. Could remove the access plate, lock, make adjustment, bend the lock, and put all back together in about 10 min, but didn't think I could deal with the linkage that quickly, as I've never done it before.

    Going to try the upper linkage rod today and will let you know how it goes.
     
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  4. bender

    bender Road Train Member

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    Well, since you weren't able to adjust the linkage and you've been running you had to have done that or something similar lol. I've had to do that a time or two to get someones truck through a days work so it could later be done properly.
     
  5. 55_cans

    55_cans Light Load Member

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    Well I backed the adjustment ring off counter-clockwise, then tried to lengthen the linkage, but ran into a problem. Most linkages I've seen are right hand thread on one end, left hand on the other, so when the lock nuts are loosened, you can turn turn the linkage, then relock it. You don't have to take apart any linkage joint.

    On mine the linkage is curved to clear the cab frame, so you can' turn it. I took the most accessible joint apart, and unthreaded the pillow block joint out of the linkage, and found only about 3/8" of thread left. Not enought to lengthen the linkage (I think). I was going to try the less accessible end to see how much adjustment thread is available there. I don't feel good about any less than 1/4 " of thread being locked into the linkage.

    Before I go on, am I thinking about this right? Lengthen the linkage to restore the freeplay?

    If so I guess it's time for a clutch. The part number is old 129018.4.K88. I think this crosses to a 15-1/2" 129018-74 (10 spring-1650lb torque) or 129018-81 (8 spring-1400lb torque). Have to go back and count springs.
     
  6. 55_cans

    55_cans Light Load Member

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    Mine's an 8 spring - so the cross must be 129018-81 1400lb. Does this make sense?
     
    Last edited: Sep 19, 2012
  7. bender

    bender Road Train Member

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    What truck do you have? There are different types of linkage adjustments depending on make of truck.
     
  8. 55_cans

    55_cans Light Load Member

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    Freightliner FLD120, Series 60, 15 Speed EF, Gravel Truck.
     
  9. bender

    bender Road Train Member

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    The linkage rod that you want to lengthen is the final rod that connects to the lever on the cross shaft at the transmission. That should be the rod with the bend in it for clearance. Remove the linkage rod from the truck, free up both ends so you can easily make adjustments when you put it back on.

    If you make adjustments on other parts of your linkage it can change the geometry of your clutch pedal operation (leverage/breakover point).

    Set your 1/2" gap between release bearing and clutch brake using internal clutch adjustment, then adjust your linkage rod for 1/8" gap at the release yoke fingers to the release bearing pads.

    Replacing the clutch will not correct the problem, you'll just have a new clutch with the same problem lurking around the corner.
     
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  10. 55_cans

    55_cans Light Load Member

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    Thanks for the info. Its a pain to get to the tranny lever end, but I did. I removed the linkage. It's a 5/8" square bar with threaded holes drilled in each end. Into these holes screw in threaded pillow block eyes that are used to bolt the linkage to the tranny lever and pedal level arms. A pillow block eye is my terminology to describe an eyes that has a greaseable sphrerical bearing insert. This lets the linkage rotate slightly (+/-15 degrees) off axis.

    Both threaded eyes only have 3/8" thread engaging with the linkage before the lock nut tightens. I can safely lengthen the linkage by leaving only 1/4" thread engaged before the eyes are locked. This only gains a rod length of 1/4".

    Am I thinking right, that I have to lengthen this linkage to increase the free play?

    The only way I see to gain more length is to replace the 5/8" square bar with a longer piece, or purchase new eyes with a longer threaded end.

    The linkage setup looks like this :)) forgive my graphics):

    O pivot for clutch pedal lever
    | clutch pedal lever arm
    |
    O---------------------------O
    .............. Linkage .............. |
    ........................................ | cross shaft lever arm
    ........................................ O cross shaft pivot

    Moves <----- this way when clutch engaged.

    PS The linkage bar looks like it was repaired by a prior owner, the middle has a welded section.
     
  11. Gear head

    Gear head Medium Load Member

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    or have someone weld a section of pipe in middle.
     
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