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Changing Yokes... how tight?

Discussion in 'The Garage' started by blazerpro79, Oct 30, 2005.

  1. blazerpro79

    blazerpro79 1/2 ton status

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    Hey guys, I'm about to go change out my yokes on my 12 bolt rear and np203 and I need to know how tight to torque my yoke bolts. Thanks in advance.
    -mark
     
  2. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    I'm about to do the same thing. There is no exact answer, because technically you should set up the gears again.

    If I was putting the same yoke back on, I would mark and the pinion and nut correspondingly and then count the number of turns to get it off. Then put it back on with the same number of turns and lining the marks up.

    But, since the yoke is different I don't think that would be exactly accurate.

    I'm paranoid about this kinda thing, so I've come up with a proceedure I'm going to try.

    I'm going to mark it like outlined above and completely remove the yoke.

    Then I'm going to re-install the old yoke lining up the marks and counting the turns. I'll use my deflecting beam torque wrench to figure out the torque it takes to line the marks back up.

    Then I'll pull it back off again and install the new yoke to the torque setting I found above.

    I'm also replacing the seal while I'm at it.

    Randy's Ring & Pinion recommends putting some oil on the washer so it can turn if needed and use red locktight for the nut.

    I also read something about using Permatex non-harding sealer on the splines, but I haven't been able to confirm that yet.
     
  3. 1977k5

    1977k5 3/4 ton status Vendor

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    I wouldn't change the yoke on the 12 bolt if you don't know how to set up gears, I don't think you wil be happy with the result even if you try to count the turns and whatnot. The torque at the t-case should be about 150 ft. lbs.
     
  4. blazerpro79

    blazerpro79 1/2 ton status

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    the yoke just unbolted and rebolted up... what do you guys mean about the gears? i didnt have to open the diff up or anything.
     
  5. muddybuddy

    muddybuddy 3/4 ton status

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    i believe improper torqu effects how the pinion lines up with the gears. if not done properly, it can destroy ur gears. im not 100% sure tho
     
  6. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    The nut and the yoke you removed are what hold the pinion in the differential housing.

    When gears are installed the nut is torqued down to crush the crush sleeve. That is what sets the pinion bearing preload. Preload is basically how tightly the bearing are pressed into the races which provides some rolling resistance.

    So by removing the nut and yoke, you could potentially change the preload, and possibly even the pinion depth.
     
    Last edited: Oct 31, 2005
  7. 1977k5

    1977k5 3/4 ton status Vendor

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    And having an improperly set pinion bearing preload could make the rear end seize up on your first drive down the street! You could get lucky and your rear end may last a little while (it's life is almost certainly shorter because without resetting the pinion bearing preload it is wrong).
     
  8. 85mudblazin

    85mudblazin 1/2 ton status

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    I doubt you can put enough force on it to crush the sleeve further with a simple ratchet.
    When i did my 14b yoke, I just pulled the nut, pulled the yoke, new yoke on, and tightened it down till it got tight. You will be able to feel when the yoke gets up against the crush sleeve.
     
  9. 1977k5

    1977k5 3/4 ton status Vendor

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    It does take a lot of force to begin crushing the crush sleeve, but once it starts it goes pretty easy. Since the rear end had already been assembled, the sleeve had been crushed. If I were to put one back together like this I would put the nut back on until I noticed the nut start to get tighter and then stop.
     
  10. Executioner

    Executioner 1/2 ton status

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    Please explain how the "nut is torqued down to crush the crush sleeve. That is what sets the depth of the pinion. "
    Thanks

     
  11. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    No...shims set the pinion depth. The crush sleeve sets pinion bearing pre-load. Crush sleeve has very little if any change on depth because the inside bearing on the pinion still sit in the cup whether the crush sleeve is torqued to hell, or on mildly tight.

    When you did that to your 12-bolt, you should've used a new crush sleeve and pinion nut. Don't be surprised when the nut backs off, the pinion falls into the diff and locks your rear end up regardless of what speed you are going. How do I know this? Personal experience. That's why I have the 14-bolt now...
     
  12. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    That's right of course.

    I fixed my original post to reflect the correct information.

    I know that just unbolting the yoke and then re-intalling it is not the official method, but I'm doing it that way based on the various methods I've been able to find.

    I suppose this is probably a better method:
    Guess it's a good thing I have a 14bolt with the right gears. :crazy: :doah:
     
  13. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Didn't mean you, guy! :D I meant blazerpro... :crazy: shoulda wrote that!! If he didn't use a new nut, he's asking for it....unless he used the chisel trick....
     

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