muncie speedo bullet and adapter 1970 Z28

Discussion in 'Transmission & Driveline Topics' started by Jeffmort, Mar 22, 2017.

  1. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    It depends upon the rear gear ratio.
    Some gear ratio/transmission combinations required the adapter because the speedometer gear combination for accurate speedometer/odometer readings didn't exist.

    If your adapter has a 1.0 on it... it's not needed. (See pic above with .824)
     
  2. COPO

    COPO Veteran Member Lifetime Gold Member

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    I've always seen them on. My 71 Z28 M22 w/3.73 gears also had it.
     
  3. jbloake

    jbloake Veteran Member

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    What does the P7 stamped on the end of the adaptor stand for ?
     
  4. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Anyone know the ratio it is supposed to have for a 3.73 rear gear? Is it the .8241?
     
  5. COPO

    COPO Veteran Member Lifetime Gold Member

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    P5 is in my 70 Z28 that came with a M20 - 1970 May (my car is a May car)
    P7 is what I had in my 71 Z28 with a M22 - 1970 Jul

    The P5 and P7 for example are date codes.
    [​IMG]
    [​IMG]
    [​IMG]
     
  6. jbloake

    jbloake Veteran Member

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    Th
    Thank You !
     
  7. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Mark,

    Good info. Thanks

    Was there a rear gear difference between the 70 and 71?

    My guess is the ratio inside is determined by the rear gear and tire size, not whether it was an m20,21,or 22.
     
  8. COPO

    COPO Veteran Member Lifetime Gold Member

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    Both my 70 (M20) and 71 (M22) Z28's has/had 3.73 gears and F60-15 tires on stock Z28 rims. The diff from 70 to 71 was a 12 bolt to a 10 bolt rear.
     
  9. jbloake

    jbloake Veteran Member

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    image.jpg
    This is from 73 and shows 373 and F60 15 and .8242
     
  10. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    Beavercreek, Ohio, USA
    Great. Thanks!. Now one more thing to find.
     

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