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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » C4 band adjustment???

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    5/10/2013 5:27 PM  #1

    Ron68
    Senior 24-7 FYI Addict

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    From: Mukilteo, Washington
    Registered: 4/01/2013
    Posts: 1,627

    C4 band adjustment???

    The 79 C4 in my 68 was not upshifting into 3rd. Checked the fluid - full and clean, was changed last summer. Put a vacuum on the hose to the modulator - held 15" just fine. It had been since 2001 since I rebuilt the transmission, and have not had any problems till now.

    I decided to adjust the low/reverse and intermediate bands. I went online - found several different numbers by others on what to set the bands at.

    My overhaul manual (C4/C5) stated to torque the intermediate band to 10 ft/lbs then back off 4 1/4 turns. It stated to torque the low/reverse band to 10 ft lbs and back off 3 turns.

    On the internet, I found: Int. - 10 then back off either 1 - 1 1/2 turns or 1 3/4 turns. L/W - 10 then back off 2 turns or 3 turns.

    My 1968 shop manual for a 68 C4 was Int. - 10 then back 1 3/4 turns. L/W 10 then back off 3 turns.

    I used those last numbers, and it seems to work just fine now. I'm scratching my head about the 4 1/4 turns back in my O/H manual.....

    What numbers do you guys use?

    68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
     

    5/11/2013 8:11 PM  #2

    Ron68
    Senior 24-7 FYI Addict

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    From: Mukilteo, Washington
    Registered: 4/01/2013
    Posts: 1,627

    Re: C4 band adjustment???

    Guess this subject is beyond most posters here.....??? No one ever adjusted the bands before??

    Oh, well - it works fine now anyhoo.Thanks for looking.

    68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
       •Thread Starter
     

    8/04/2015 8:04 AM  #3

    Don H
    Active Member

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    Registered: 8/04/2015
    Posts: 3

    Re: C4 band adjustment???

    Recently had my 641/2 C4 transmission rebuilt. Now it shihts erattic at low speed. It is fine at higher speed. Any ideas about the cause and a solution
    Don

     

    8/04/2015 9:36 AM  #4

    rmousir
    FYI Addict

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    Registered: 4/01/2013
    Posts: 156

    Re: C4 band adjustment???

    Its been a really long time since I did this.  I think its been 4 years since I rebuilt my last c4.  I think your right with the 1 3/4 turns.  I'd have to check my vids to confirm..

     

    8/04/2015 10:26 PM  #5

    351MooseStang
    FYI FORD Member

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    From: Brookings, Oregon
    Registered: 4/03/2013
    Posts: 91

    Re: C4 band adjustment???

    The difference between the two adjustments you are finding is that the C5 has a finer thread on the band adjuster, requiring more turns to move it out the same distance as the fewer turns required on the coarser threads of the C4 adjuster.

    Third gear hanging up can be related to either the vac modulator or the governor. You mod may be holding vacuum but if it's full of 'goop' from not having a loop in the line, it can hold pressure and not be able to move very well. A good way to check the mod is to pull it and the pin and then put the pin back into the mod. Then hold the mod and press the pin against a hard surface to push the diaphragm in back to its seat. If any 'goop' comes out of the vacuum nipple on the valve, replace it.

    Just something I've run into in the past. Good luck!

    Last edited by 351MooseStang (8/04/2015 10:27 PM)

     

     

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