TH400 Front band upgrade to 1.25"??

Discussion in 'Transmission & Driveline Topics' started by Da_Raabi, Dec 1, 2017.

  1. Da_Raabi

    Da_Raabi Veteran Member

    843
    70
    Jan 19, 2011
    Daytona Beach, FL
    Has anyone ever used the "upgraded" 4L80E front band in a TH400? Stock the TH400 uses a 1" wide front band, the 4L80E uses a wider "high-energy" 1.25" band.

    From what little I can find online, it looks like the 4L80E band can be used, as long as a 4L80E Servo pin is used too. ACDELCO p/n 24223081.

    Has anybody done this and had any issues? I've seen it recommended in a few places, with mention of needing to measure clearance. What is this referring to?
     
  2. camaro71/holland

    camaro71/holland Veteran Member

    858
    16
    Aug 27, 2003
    The Netherlands
    Yes, I have. Only got a pic of the rear band. Looks the same, a hwy duty type.

    Didn't install a 4l80 pin. Your trans doesn't know what pin it's running. Just do the air check and see if it's holding or not and or it's binding without air and adjust the pin accordingly.

    More important, check the flatness of the drum, or it will slip/burn soon after install.

    IMAG0721_zps2c7e6b70.jpg
     
  3. Da_Raabi

    Da_Raabi Veteran Member

    843
    70
    Jan 19, 2011
    Daytona Beach, FL
    Interesting. I thought the longer 4L80E pin was needed for the front band. This is a tough one because there is very little info out there on the subject.

    What do you mean by "flatness" of the drum?
     
  4. camaro71/holland

    camaro71/holland Veteran Member

    858
    16
    Aug 27, 2003
    The Netherlands
    This is what I meant. The dish in the drum from the band running on it. I could turn it flat again. Then welded some material to the tip of the pin, then grinded it to correct length.
    IMG_3282.jpg IMAG0552_zps09d93a1d.jpg IMAG0553_zps83dce028.jpg
     
    Last edited: Dec 1, 2017
  5. Da_Raabi

    Da_Raabi Veteran Member

    843
    70
    Jan 19, 2011
    Daytona Beach, FL
    Has anybody ever increased the number of springs in the intermediate apply piston? Stock, mine had 3 retained with a plastic retainer, but it looks like it could hold 6 or even 9. What effect would this have?

    The B&M transkit (which I'm not using, just referencing) recommends the upgrade. I just cannot find any information on what effect it would have.
     

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