Find gear ratio on pete 389

Discussion in 'Peterbilt Forum' started by Wespipes, Aug 30, 2020.

  1. Wespipes

    Wespipes Road Train Member

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    2019 pete 389. I was told its 3.25. I cant find it anywhere on the truck. Not in the glove box. Not on the door. I goggled and somewhere said to crawl under your rear end it should be stamped there. That says 416. Nothing else stamped anywhere. Any idea? If not ill call pete tomorrow and try to find out with my Vin. Also saw someone say you can tell by your rpms? I'm at 1350/1400 in 18th gear going 70 20200830_173950.jpg
     
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  3. pavrom

    pavrom Road Train Member

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  4. singlescrewshaker

    singlescrewshaker Road Train Member

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    What size rubber you running.?
    41" is tall 22.5" or low pro 24.5"
    Screenshot_20200830-192542_Samsung Internet.jpg
     
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  5. Wespipes

    Wespipes Road Train Member

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    I'm running tall 24.5's
     
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  6. Wespipes

    Wespipes Road Train Member

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    Tire hight is 44
     
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  7. singlescrewshaker

    singlescrewshaker Road Train Member

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    I put 43" in one because usually an inch of tire height is lost in my experience from the weight of the truck squishing them down. If you can narrow down the rpm to 1350 or 1400 you can get a closer idea of which ratio is actually correct. As long as the clutch is not slipping rpm should be constant per given road speed. Spicer gear ratio calculator in Google is where I entered these values..

    Screenshot_20200830-193744_Samsung Internet.jpg Screenshot_20200830-193600_Samsung Internet.jpg Screenshot_20200830-193535_Samsung Internet.jpg
     
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  8. pushbroom

    pushbroom Road Train Member

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    Whats the last 6 of the vin? There should be a tag on the front of the pumpkin, may be covered in paint
     
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  9. Wespipes

    Wespipes Road Train Member

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    612782

    There is a tag. Covered in paint. I couldn't see any markings on it though
     
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  10. Dino soar

    Dino soar Road Train Member

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    Get a rag with thinner and wipe it down.

    If you can't read that one do the same with the other rear.

    Sometimes a soft wire brush helps.
     
  11. Wespipes

    Wespipes Road Train Member

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    Well peterbilt HQ was surprisingly unhelpful. I'll try a dealership. I suppose
     
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