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Auto Query - Forced Downshift

Discussion in 'Engine & Transmission' started by phantom, Jul 6, 2014.

  1. phantom

    phantom Member

    Messages:
    363
    Location:
    Rural NSW
    Hi all,
    I have a '75 with an auto transmission, recently it refuses to force a downshift in gears, for example, if you are going uphill you would often put your foot down which would force the transmission to change back from (say) 3rd to 2nd. It doesn't want to do this now, it will still change gears as normal but I can't force a change like this.

    I've heard conflicting stories over what part of the assembly enables the forced shift, either a controller somewhere on the transmission, or a button under the accelerator pedal. The pedal button makes sense however the button there doesn't seem to contact on anything, so I can't see how it would function. As stated the car used to force shift fine, so its just decided now to play up.

    If anyone has good experience in this area and has some advice I would be very appreciative, I don't like holding up traffic hugely on the highway and planning trips around the hills isn't an option!

    Thanks all.
     
  2. Luckyphil

    Luckyphil Well-Known Member

    Messages:
    5,991
    Location:
    Gosford
    Till you sort the problem you can always use the gear selector to downshift.
     
  3. Abby.75

    Abby.75 Member

    Messages:
    291
    Location:
    Adelaide
    1404625968115.jpg

    Its the kick down switch... it's adjustable. Abby didn't have one at all when I got her and the pedal was all wrong and attached with a door hinge...
     
  4. Grantus

    Grantus Well-Known Member

    Messages:
    15,748
    Location:
    Southern ACT
    Hey Bruce,

    If it's the original 39 year old switch....... it may have simply failed, and time for a replacement. :rolleyes:
     
  5. phantom

    phantom Member

    Messages:
    363
    Location:
    Rural NSW
    Thanks all, so this is the switch behind the accelerator pedal? If so, what does it 'contact' to make the change? How does the pedal know the difference between simply accelerating along the road, and trying to climb a hill?

    My switch doesn't look like it will touch anything, is there something under the pedal (i.e. on the floor?) that is supposed to contact the switch? If anyone has a photo or diagram I'd be hugely appreciative.

    Grantus, use it is probably the original, now I just have to find out how it works, and find a new one.

    Thanks everyone.
     
  6. Hooch n Lol

    Hooch n Lol New Member

    Messages:
    96
    Location:
    Burpengary, QLD
    My switch will only kick down if the pedal is hard on the floor, the switch is connected to a solenoid on the gearbox that changes the gear.
    Just check the voltage over the switch when it is open and closed - at least that will let if the switch is working.
     
  7. 1500king

    1500king Well-Known Member

    Messages:
    1,545
    Location:
    Adelaide, SA
    Hi,

    The kick down micro-switch(Pictured thx Abby.75! :) )is encased in a small frame under the pedal. It is hinged at the top end and sprung at the bottom end. The pedal "dog leg" linkage passes through the mid section of the case where as pressure is applied to the pedal, enough to overcome the spring. The casing that houses the switch is pushed against the pedal. The switch button then touches the underside of the pedal and activates the kick down solenoid in the trans. The usual culprits are worn linkages under the pedal and poor wiring connections and they all need to be checked. The solenoid can be checked by checking its resistance at the spade terminal for it on the trans.
     
  8. phantom

    phantom Member

    Messages:
    363
    Location:
    Rural NSW
    Thanks all, I'll get this switch looked at and will see if I can find a replacement in the meantime. I appreciate everyones info.
     
  9. phantom

    phantom Member

    Messages:
    363
    Location:
    Rural NSW
    I can't locate these switches anywhere, and am considering working an alternative until I can find a replacement item. I'm looking at running wires off the pedal to a push switch on the dash, like a horn button. Any ideas if this would work? I know I can shift with the lever but I would rather try to get the auto shifter functional. Thanks.
     
  10. Grantus

    Grantus Well-Known Member

    Messages:
    15,748
    Location:
    Southern ACT
    Bruce....got your PM & email, and yes, all good. I'll have to find time for a long reply, or maybe I'll just give you a ring for a chat, and save my typing fingers.....


    Back on topic - where can one source another switch mech for this bus? :rolleyes:
     
  11. john doherty

    john doherty Well-Known Member

    Messages:
    798
    Location:
    adelaide
    Kingo,

    I continue to be incredibly grateful for firstly, your membership and participation in this odd group of earthlings and secondly, your willingness to contribute in such an amazingly concise and ever so helpful manner. Are there any more Martian's on the planet like yourself, or are you just a one-off? I have never seen anyone so consistently…………correct......(Apart from myself that is?)
    Very warm regards
    JD:cool:
     
  12. john doherty

    john doherty Well-Known Member

    Messages:
    798
    Location:
    adelaide
    Kingo,

    I continue to be incredibly grateful for firstly, your membership and participation in this odd group of earthlings and secondly, your willingness to contribute in such an amazingly concise and ever so helpful manner. Are there any more Martian's on the planet like yourself, or are you just a one-off? I have never seen anyone so consistently…………correct......(Apart from myself that is?)
    Very warm regards
    JD:cool:
     
  13. Abby.75

    Abby.75 Member

    Messages:
    291
    Location:
    Adelaide
    Nope he's a one off... lucky for me....and the combined menagerie...Mars must be missing him....

    Abby.75
     

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