8.5 rebuild and upgrade. Advice and guidance needed

Discussion in 'Transmission & Driveline Topics' started by Camaromurph, May 17, 2020.

  1. Camaromurph

    Camaromurph Veteran Member

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    Cool. Thanks for all the suggestions everyone. My son and I were having a measurement system accuracy discussion when doing our backlash checks. Having a good repeatable set up seems important. The one piece that I don't ever see addressed is if the movement of the dial indicator shaft should be parallel with the "rotation" of the ring gear (parallel with the ring gear bolt face) or perpendicular to the gear. Does that make sense? FBird - I know this is exactly what you are getting at above and I just want to make sure I understand what you were saying.
     
  2. big gear head

    big gear head Veteran Member

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    Dial indicator should be perpendicular to the center line of the ring gear. Imagine that you are trying to measure the maximum amount of ring gear movement.
     
  3. Camaromurph

    Camaromurph Veteran Member

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    Okay. I reset pinion preload down to 20 in-lbs. Now I’m onto backlash. I seem to have a good measurement set up but think I am seeing more variation around the ring gear than I should. How much backlash variation is good on these AAM gears 2 cut gears. I seem to have about 0.004” variation as I check around the ring gear in different places.
     
  4. big gear head

    big gear head Veteran Member

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    That seems like a lot. Set the indicator up on the back side of the ring gear flange and check it for run out. If it has more than .003 then you might want to replace it. If you have enough room to set it up on the back side of the ring gear that would be even better.
     
  5. Camaromurph

    Camaromurph Veteran Member

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    Roughly 0.007” on both. A little hard on the ring gear flange as I had to skip the dial indicator over each bolt. This is a new Eaton Truetrac and new AAM gears.
     
  6. big gear head

    big gear head Veteran Member

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    If the ring gear flange has .007 run out then I would be contacting someone about getting a replacement. That's too much.
     
  7. Camaromurph

    Camaromurph Veteran Member

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    Yeah, I started that process after my last post last night.

    Since I bolted the ring gear up to this distorted flange do you think it needs to be replaced as well or will it spring back when removed and be Okay?

    also of interesting note is it wasn’t a single distortion. Dial indicator went

    0”-0.005”-0”-0.007” as you made the full 360 degree sweep around the gear.
     
    Last edited: May 29, 2020
  8. big gear head

    big gear head Veteran Member

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    The ring gear should be fine. I would remove the gear and then check the differential. It's possible that the gear is the problem. The gear may have warped when it was heat treated.
     
  9. Camaromurph

    Camaromurph Veteran Member

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    Okay, so the good news (I guess) is I took the ring gear off and reinstalled the differential without it and there is less than 0.0005” runout without the ring gear.

    I will file the ring rear and differential surface to make sure there are no burrs. And retry the assembly.
    Can I reuse the new ring gear bolts or do I now need new ones?
     
  10. camaro71/holland

    camaro71/holland Veteran Member

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    Don't forget to file the differential flange as well, you can't tell where the burrs are located.

    You can reuse the bolts if they came new with the R&P set. If 40+ years old, I wouldn't save a penny there.
     

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