DD12 transmission wont go in gear when hot

Discussion in 'Trucks [ Eighteen Wheelers ]' started by The_Great_Corn, Mar 10, 2019.

  1. The_Great_Corn

    The_Great_Corn Bobtail Member

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    When I'm in the mountains and the temperature gets up around 190 the transmission will clunk trying to shift and go into neutral for a second then after a couple tries it will go in gear. It's frustrating and dangerous when it slows me down too much. Anyone else have this problem? Someone was telling me these Transmissions are junk. Going across I-68 in Maryland I have to take a couple hour long breaks to let it cool down.
     
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  2. Lazer

    Lazer Light Load Member

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    check the transmission oil level. hope the last time truck was serviced the correct oil was used.
     
  3. Tombstone69

    Tombstone69 Heavy Load Member

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  4. The_Great_Corn

    The_Great_Corn Bobtail Member

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  5. Tombstone69

    Tombstone69 Heavy Load Member

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    Does it have a hydraulic clutch?
     
  6. Animosus

    Animosus Medium Load Member

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    It's a DT12. So hopefully it has a Concentric Pneumatic Clutch Actuator.
     
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  7. D.Tibbitt

    D.Tibbitt Road Train Member

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    i have the same tranny only i have a 16 cascadia.. man its a piece of junk.. i have the same problem as u but mine does it when its cold... sometimes it wont go into 7th gear, usually first thing in the morning if i havent got the engine warmed up to about 150... its incredibly annoying, i dont know why they just cant leave these stupid autos out of a truck, they do not belong in a truck
     
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  8. Tombstone69

    Tombstone69 Heavy Load Member

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    I guess automatics are not so.
     
  9. Brandt

    Brandt Road Train Member

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    My 2017 DT12 has 308,000 miles and not any problems yet. It works in all temps. I think it would hit 215F pulling a big hill in the summer. It was never a problem. Just guessing but the clutch thing it has might be going out
     
  10. Tombstone69

    Tombstone69 Heavy Load Member

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    I believe what they have is called an inertia brake and it works like a clutch brake. When that goes the computer doesn't know when to shift, those computers are so lame, you just can't find a good one anymore.
     
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