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Alternator V-belt pulley slipping when swapping to 3G alt

Discussion in '6.9L IH & 7.3L IDI Diesels' started by BlindAmbition, Feb 14, 2021.

  1. franklin2

    franklin2 Full Access Member

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    Addressing the title of this thread, a single v-belt will not support the power required by a 130amp 3G alternator at full output. You can expect a belt squeal at at start-up using a single v-belt. Hopefully you can get a dual v-belt setup going.
     
  2. frankenwrench

    frankenwrench overkill is under rated!

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    Mine has never squealed at any point even with all lights and heater on high. I am still using v belts as well. No shim, no grinding. Just bolted on and modified the wiring. I have 3 trucks with this mod. 88, 89, and a 91.
     
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  3. BlindAmbition

    BlindAmbition Full Access Member

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    Figured out why it was rubbing - I probably lost a washer when painting it.
    New Old
    IMG_20210217_163329469.jpg IMG_20210217_163344421.jpg
     
  4. BlindAmbition

    BlindAmbition Full Access Member

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    How would one go about running a second belt? I see reference to it on just about every v-belt 3g alternator thread but haven't seen anyone actually do it. Searched to no avail through quite a few threads so far this morning with no results.
     
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  5. RetiringColt

    RetiringColt Full Access Member

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    Here's a pic from the internet because I'm away from my truck, but you can see the two belts. Inside belt is for driving the alternator from the crankshaft and the outside belt is driving the vacuum pump from the alternator. Really only the inside belt drives the alternator. The outer belt is a parasitic draw from the alternator to turn the vacuum pump. Screenshot_20210219-021622_Chrome.jpg
     
  6. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    I have had the same experience with my 89. Only belt squeal has been from mashing through a large puddle.
     
  7. TNBrett

    TNBrett Full Access Member

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    The other thing worth mentioning is that the two grooves on the original pulley are not the same width. The vacuum pump belt is narrower than the alternator belt.


    Sent from my iPhone using Tapatalk
     
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  8. Isaac Ristow

    Isaac Ristow Full Access Member

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    I have no belt squeal with my 130 3g
     

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