904's Keep Failing on 67 Motor

Transmission and Drivetrain Tech

  1. 540slant6

    540slant6 Mopar SB Ripper

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    So I have a 67 spec forged crank 318 in my Duster with a 67 spec 904 Auto. However, the motor came from a Sattelite that had a 727. So I changed the flex plate and have now destroyed 2 904's. The first trans broke off the convertor shaft clean at the welds. The second one is now puking fluid out the front and is doing the same thing.

    My theory is that the 67 motor crank is only drilled for the larger 727 convertor snout. So the smaller 904 snout is walking in the crank and destroying the 904 sized convertors? Meaning that the 67 crank is drilled larger than the 904 convertor snout. I know that 67 is a weird transition year so any input is greatly appreciated.

    I'm at my wits end and running out of money......
     
  2. Plymouth 65

    Plymouth 65 Floorable Deplorable

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    I believe you are correct. The pilot on the 67 crankshaft is larger. I'm not sure what year 904 converter you are using but if it an early one the snout is the small diameter. They make a bushing that presses onto the small snout converters. If you are getting a new converter just get the one with the larger snout. I believe 68-72 904 converters used the large snout. Hope this helps !
     
  3. 540slant6

    540slant6 Mopar SB Ripper

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    That does help! I had a hunch that the problem was the 67 crank. Now I need to fine the bushing to install the smaller convertor into the larger 67 crank.

    Thanks for your input!
     
  4. dart4forte

    dart4forte FABO Gold Member FABO Gold Member

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    Common issue when using a 67 and earlier converter in a newer 318 crankshaft with the larger crank register. A buddy of mine who happens to be a member here and an accomplished machinist built me a spacer that fits over the converter snout. The spacer ID fits over the snout while the OD of the spacer fits the crank register.

    In the interest of respecting his identity and privacy I cannot give you his information however he does follow FABO so he may see this thread and offer his assistance.

    If not, any machinest with a lathe can fix you up. All he needs is the converter snout OD, the crank register ID and depth along with an explanation from you what your problem is.
     
  5. 540slant6

    540slant6 Mopar SB Ripper

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    Thanks guys, I'm assuming no one makes a 904 converter with the larger snout so it sounds like the microsleeve is my only option.
     
  6. Plymouth 65

    Plymouth 65 Floorable Deplorable

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    Incorrect, just get a 904 convertor from a later model year 68-72, they have the larger snout diameter.
     
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    • Locomotion

      Locomotion Well-Known Member

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      Nope! Spline count is different between the older, small snout converters and the newer bigger snout versions. They do not interchange.

      (The lock-up converters don't interchange with anything older as well.)
       
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      • 65Val

        65Val Average Length Member

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        • Thanks! Thanks! x 1
        • Plymouth 65

          Plymouth 65 Floorable Deplorable

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          I stand corrected, the trans input shaft spline is different. Gonna have to go with the bushing !
           
        • MOPAROFFICIAL

          MOPAROFFICIAL Well-Known Member

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          Any convertor/ trans shop with a source for one can put '67 and earlier guts into a '68- up convertor
          Earliy spline count is like 19....while the '68 -up are 27.
          If it were the other way....either the crank register would need turned larger or the trans would need changed.
           
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          • Charrlie_S

            Charrlie_S Well-Known Member

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            Easiest way is the adapter bushing. I have them for sale $25.00 shipped
            Send me a PM, if interested.
             
          • 540slant6

            540slant6 Mopar SB Ripper

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            I'll send you a convo shortly!
             
          • 65Val

            65Val Average Length Member

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            Sorry Charrlie_S....I didn't know you had these as well.....:thumbsup:
             
          • 540slant6

            540slant6 Mopar SB Ripper

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            So I still have the vibration and will check the motor and trans mounts. I guess the next item is to check my stock ballancer since it's the original front 67! May be time to upgrade.
             
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