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GM 12 BOLT REAR END PROBLEMS Need Some Help Please

Discussion in 'The Garage' started by doctor4x4, Nov 24, 2003.

  1. doctor4x4

    doctor4x4 1/2 ton status

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    anybody have a blown up view of one or a page that teaches ya how to set up the proper ring and pinion pattern
    here's what i got
    i bought the complete axle allready assembled but the guy must have set it up wrong as it growls at me when i take my foot off the gas but aceleration is fine no noise
    all parts are new well less then 100 miles on em
    4:10 carrier with thickset 4:56 gears
    and a Detroit Easy Locker
    thanks in advance
    Randy
     
  2. gzzgfw

    gzzgfw 1/2 ton status

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    Here's what I'd do.
    Pull the cover and check backlash in 3 or 4 places around the ring gear. Should be 8-12 thousanths. If this is OK then check gear pattern on the drive side of the teeth, if you don't have marking compound use some grease. Should be in the middle to the toe end (toward the ID) and in the middle of the tooth up and down (top and root of the tooth).
    I wouldn't think that a bearing would be making your growling, or it would do it all the time. Good luck -Mark
     
  3. TrcksR4ME

    TrcksR4ME 1/2 ton status

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    Bad carrier bearings can exhibit these noises, but it seems unlikely if everything is new. I would guess the gears are set up wrong and that it is possible that this has caused the bearings to go bad /forums/images/graemlins/crazy.gif
     
  4. ZootownK5

    ZootownK5 Registered Member

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    i bought a 12b from a guy a while ago and it did the same thing. thought it was a bad pinion bearing, but ended up being a loose pinion nut. i rebuilt the whole thing anyway with lower gears and an lsd. mine exhibited the same symtoms as would a bad pinion bearing.

    Ryan /forums/images/graemlins/k5.gif
     
  5. doctor4x4

    doctor4x4 1/2 ton status

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    its times like this when im very glad and gratfull im a member
    thanks guys
    if any body has a link to a break down of 1 to make sure who ever put it together did it right
    i would really appricate
    R
     
  6. R72K5

    R72K5 Banned

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    find one of those 63-82 GM truck service manuals, they will have all the 12 bolt diagrams and info in them, any of those years vans blazers burbs pickups 5 and 10 series 8.875" ring gear, i dont currentyl know of any 12 bolt exploded view diagram online for 12 bolt truck 8.875"

    someone here might have a scanner and could scan you a diagram or more out of a service manual, i have some but no scanner /forums/images/graemlins/frown.gif

    noise like that is going to be bearing or incorrect backlash settings, most likely pinion shim problem, or overtightened the pinion crush sleeve which brings pinion to far forward and away from ring gear causign backlash excessive
     

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