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Driven gear issues

Discussion in '6.9L IH & 7.3L IDI Diesels' started by frankenwrench, Sep 7, 2019.

  1. frankenwrench

    frankenwrench overkill is under rated!

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    My sister just bought an 89 f350 drw 7.3 idi with 1st Gen Banks and c6. She currently has 4.10 rear end. She wants the 3.73s for better fuel economy and she just graduated high school so she won't be doing much towing if any but has her nose up at the 3.55s I have. I would love to know what junkyard vehicle would have the ring and pinion I need and what driven gear (end of speedometer cable) I would need so that the speedometer on the dash is still correct. Any help would be appreciated.
     
  2. snicklas

    snicklas 6.0 and Loving It!! Staff Member

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    3.73 were not stock on ANY IDI era truck. They didn't start until the 99+ SuperDuty, an might not have started till the 6.0 in 03 (My Excursion has 3.73's.
     
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  3. frankenwrench

    frankenwrench overkill is under rated!

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    Yessir. I had to pull my whole rearend off of a 2001 super duty. She was wanting just the ring and pinion for the dually truck now she just wants to swap the rearend from another 99 to 04 dually. But I guess the only issue remaining is finding the plastic gear for the end of her speedometer cable that goes into the c6 transmission to keep her dash speedometer correct with the new gearing.
     
  4. renjaminfrankln

    renjaminfrankln Supporting Member Supporting Member

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    Bronco Graveyard should have them
     
  5. frankenwrench

    frankenwrench overkill is under rated!

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    Would they know which one I need?
     
  6. u2slow

    u2slow Plan B

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    I'd do some actual speed checks after the ratios change. Might not be worth correcting. Most factory vehicles read high for the speed they are actually going.
     
  7. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    I found a 5 pack on Ebay that comes with all the common colors/tooth counts. It was cheap like $25.
    Worked good for my 3.55 gears but i honestly cant remember what color I used. It all depends on how many teeth your drive gear has, I think IDIs got 8 teeth, it's a yellow gear. Mine was pretty trashed and needed to be replaced in order to make the speedo work. The new speedo gear was physically smaller than the one it replaced and got eaten up a bit by the bad drive gear so watch out for that!

    I'm glad I got the 5 pack so when I switch in bigger tires later I'll have a gear for that too. :Thumbs Up
     
  8. frankenwrench

    frankenwrench overkill is under rated!

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    Do you have a link by chance?
     
  9. The_Josh_Bear

    The_Josh_Bear Full Access Member

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  10. frankenwrench

    frankenwrench overkill is under rated!

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    Outstanding! Thank you man!
     

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