Gearbox / Clutch Help Needed

Discussion in 'Mech Tech' started by Dpoints, Dec 22, 2021.

  1. So, as you probably know, I'm rebuilding a 73 bus - engine is purring like a kitten (touch wood), I bought a used gearbox, and fitted a new clutch cable and Bowden tube in a new Bowden tube bracket .
    I've never driven a bus before, so I'm not 100% on the position of the gears / reverse. I've spent the morning tightening the butterfly nut but I cannot find a gear. I'm just getting the crunch noise. Should I place some washers or a nut in front of the butterfly nut to apply more tension? The pedal is not bottoming out.
    I'm guessing, I've not over tightened as this would permanently separate the clutch?
    Is there something more untoward going on here? Thanks
     
  2. Baysearcher

    Baysearcher [secret moderator]

    They quite often have a stack of washers under the butterfly nut.
     
  3. Zed

    Zed Gradually getting grumpier

    The pedal should bottom out. If not you over-tightened and you would expect the clutch to slip once in gear, but it should not crunch, so...
    Did you forget to fit the clutch release bearing?

    upload_2021-12-22_15-35-20.jpeg
     
  4. There was a clutch release bearing (resembling your photo) that moved around a cylinder at the back of the gearbox and is controlled by the lever. I guess I will try washers tomorrow. Just find it strange as its a new cable.........
     
  5. Zed

    Zed Gradually getting grumpier

    If the pedal won't hit the floor, it sounds like you already have the cable too tight, so... something else going on.
    If your bowden tube isn't a nice S shape, washers on the tube at the GB end is the way forward rather than under the butterfly nut.
     
    77 Westy likes this.
  6. sorry, my terminology is wrong. The pedal does go to the floor without too much resistance and feels it could go further hence why I thought washers would help.
    How should the Bowden tube look? It is over the end of the tube that runs front to back and is in the bracket that attaches to the gearbox, so I assumed it was 'bent' correctly as the bracket is at the rear of the tube?
     
  7. 77 Westy

    77 Westy Supporter

    It should look like the pic. If the tube is too straight add washers on the end at the bracket on the gearbox.
     

    Attached Files:

  8. before the bracket of after the bracket?
     
  9. Zed

    Zed Gradually getting grumpier

    Before, it's common to have to do this, I have half a dozen on mine - M12 IIRC
    Not exactly the same, but like this...
    [​IMG]
     
    DubCat likes this.
  10. Just wondering .... Is there a slight length difference between L/R hand drive cables ??

    :hattip:
     
  11. Last edited: Dec 23, 2021
  12. So, I tried the washer trick and still no joy. I'm guessing the gearbox is knackered which means pulling the engine and driveshafts.
    ARGHHHHHHHHHHH
    Any last ideas before I combust?
    Cheers
     
  13. Dubs

    Dubs Sponsor supporter extraordinaire

    Take the cable out and measure the length, then compare it on JK website, which helpfully states the lengths in their listings.
     
    Lasty likes this.
  14. mikedjames

    mikedjames Supporter

    The clutch operating position has basically nothing to do with the gearbox internals, but it does depend on the distance between the clutch release cross shaft and the clutch operating fingers - as they are opposite ends of the bell housing.

    It is possible you have the wrong kind of clutch on the engine - there is an older clutch design, which uses an additional spacer ring between the throwout bearing and the clutch, if the engine and clutch arrived together they could be older than you think.. The clutch will never disengage in that case, as the throwout bearing cannot reach the clutch spring fingers.

    (or the clutch is just a lump of rust fused together)

    Simple check on gearbox : Jack up one wheel with the engine stopped. Now engage a gear without using the clutch. The raised wheel should be hard to rotate. Then select neutral and check the wheel rotates freely.
    Repeat for all the gears.
     
  15. Zed

    Zed Gradually getting grumpier

    Still not tight enough?
    What dubs says...
    And/Or
    The way to set the clutch cable is by using your HAND on the pedal. This way you can feel what is happening. Press the pedal, note where resistance is felt. That should be after about 1" of pedal movement. That first inch is pedal against the spring on the clutch arm and light. After that the release bearing contacts the clutch and the resistance felt is the clutch springs which is much heavier when judged with your hand. Thusly this point is quite easy to judge with your hand. If it's happening much further down the cable is too loose. IME if you have 2" of play the gears still won't crunch if you push the pedal right to the floor. So, check it out by hand not foot to judge what's happening.
     
    Faust and snotty like this.
  16. Thanks guys, I'll have a cuppa and reconvene later this afternoon and let you know
     
  17. So, with the rear wheel jacked up (I haven't fitted the second drive shaft yet) and engine off, the wheel spins freely in all gears without using the clutch.
    Do you think the clutch is wrong?
     
  18. Zed

    Zed Gradually getting grumpier

    It will do that, that's the diff in action. Don't let Mike scare you - read his posts, he's off the wall prophesising outlandish uncommon doom as his start point. Start with simple, the clutch is dragging because it isn't operated enough.
     
    Lasty, snotty, matty and 1 other person like this.
  19. Dubs

    Dubs Sponsor supporter extraordinaire

    A pic of your Bowden tube and clutch arm might give us a clue..
     
  20. ^this. If the clutch isn’t disengaging fully, it’ll drag and engaging gears will be difficult/crunchy. Ignore weird doom-laden predictions.
     

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