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Thread: 1988 YJ front axle works when it wants too. Why?

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    Army 1988 YJ front axle works when it wants too. Why?

    I have a 88 YJ and the 4x4 works when it wants to. I shift it into 4hi and the front axle works when it wants too. Can someone explain to me what is going on and how to fix it.

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    Senior Member SavageSun4x4's Avatar
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    Being it is a direct mechanical connection the prob may lie elsewhere...I would say its in the shft lever connection either externally or internally...
    Don

    '15 Jeep Unlimited Rubicon Hard Rock...OLD SCHOOL 6 Spd Manual Trans
    17 Oaks Ranch Companies LLC

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    This spot taken? Allium's Avatar
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    its a democrat?


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    Still Growing Too! Big Green's Avatar
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    Quote Originally Posted by Allium View Post
    its a democrat?
    I like it!


    But seriously. Check the connection on the axle. Make sure the forks are engaging on the passenger side of the axle tube. The YJs have an odd setup. If you can, put the Jeep on jack stands and have a buddy shift into and out of 4x4 and check to see if it is engaging at the axle.

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    ok, since yours and mine are basically the same, heres what to look for. first check your vacume lines, from the carb to the 4x4 valve just behind it. pull it out and look inside, sometimes it can get plugged up and will need to be replaced. follow it down to the to the lower left of the fire wall just below the battery, check you electrical and vaccume connections, be sure they are all tight. next follow it down to where it splits between the transfer case and the front axel. now the connections for the front axel should collect into two locations, be sure that it don't slip off if you have your rig with the front right wheel sagging. then check the line that run along the frame to the transfer case. just on top you will barley see where it plugs in at, make sure it is tight. if all that checks out then your best bet is to look at the linkage, mine pops out somtimes as well, but it normally goes back in. if all is still good then the shift fork and internals of the front axel will need to be looked at. a good diagram of all this is in the chilton book. any other questions i will be glad to help further
    "If you don't stand for something, you'll fall for anything"
    quote from movie "sucker punch"

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    Senior Member jeepdreamer's Avatar
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    Quote Originally Posted by 19delta View Post
    ok, since yours and mine are basically the same, heres what to look for. first check your vacume lines, from the carb to the 4x4 valve just behind it. pull it out and look inside, sometimes it can get plugged up and will need to be replaced. follow it down to the to the lower left of the fire wall just below the battery, check you electrical and vaccume connections, be sure they are all tight. next follow it down to where it splits between the transfer case and the front axel. now the connections for the front axel should collect into two locations, be sure that it don't slip off if you have your rig with the front right wheel sagging. then check the line that run along the frame to the transfer case. just on top you will barley see where it plugs in at, make sure it is tight. if all that checks out then your best bet is to look at the linkage, mine pops out somtimes as well, but it normally goes back in. if all is still good then the shift fork and internals of the front axel will need to be looked at. a good diagram of all this is in the chilton book. any other questions i will be glad to help further

    X2...here is sage advice.

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    Senior Member HillBillE's Avatar
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    Yep, sounds like a vacuum line or vacuum loss problem. Early XJ's have the same type of front axle, called a Central Axle Disconnect, or CAD.

    When you shift into 4x4, a switch activates and then vacuum moves the shift fork on the front axle. If you have a vacuum leak in the system, it will work intermittenly. Usually being locked with low RPM's (high vacuum), and then disconnect with high RPM's (low vacuum)

    They make a cable to replace the vacuum set up, called a 'Posi-lock'. I think they run around $150.

    Best bet is to find the problem.

    On our plow truck ('95 Dodge 2500, exact same set up as the YJ and early XJ's) we melted a vacuum line that ran down the firewall to the T-case.

    Really sucked, considering we were in the middle of plowing out the cabin!

    Good luck!


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    Senior Member HillBillE's Avatar
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    There is another fix besides the Posi-Lock, and that is to run full axle in that side, and put a block off plate over the actuator hole.

    Requires a long side D30 axle shaft,

    A new seal,

    And a plate to block the hole. (not required, but recomended)

    Then the 4x4 will be just like the newer XJ's and TJ's.


    From Iron Rock Offroad:
    The Central Axle Disconncect system can be eliminated and replaced with this one piece axle shaft for a great strength upgrade. This requires a new axle seal. Our optional Central Axle Disconnect block-off plate allows you to remove the disconnect module and cover the opening for a clean appearance. The disconnect module could also be left in place, or removed and the opening could be left open.
    http://www.ironrockoffroad.com/Merch...egory_Code=XDT

    They have long side axles for $140, and the block off plate for $20 (though you may be able to make a plate if ya have the tools)


    As long as the people remain armed,
    government knows that it cannot rule over the people by force.
    Those who stand in defiance of unconstitutional laws
    do so out of duty, honor, oath and love of country.


    "Certified Jeep Junky!"


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    Still Growing Too! Big Green's Avatar
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    Quote Originally Posted by HillBillE View Post
    There is another fix besides the Posi-Lock, and that is to run full axle in that side, and put a block off plate over the actuator hole.

    Requires a long side D30 axle shaft,

    A new seal,

    And a plate to block the hole. (not required, but recomended)

    Then the 4x4 will be just like the newer XJ's and TJ's.


    From Iron Rock Offroad:


    http://www.ironrockoffroad.com/Merch...egory_Code=XDT

    They have long side axles for $140, and the block off plate for $20 (though you may be able to make a plate if ya have the tools)
    Since the XJ and YJ are high pinion and the TJ is low pinion, that long side would have to be from a XJ, correct?

  10. #10
    Senior Member HillBillE's Avatar
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    Quote Originally Posted by Big Green View Post
    Since the XJ and YJ are high pinion and the TJ is low pinion, that long side would have to be from a XJ, correct?
    Nope, the pinion being HP or LP won't make a difference on the shafts. Only difference will be on the ring gear and pinion themselves, as the gears are reverse cut.

    The axle shafts and carrier are all interchangable.


    As long as the people remain armed,
    government knows that it cannot rule over the people by force.
    Those who stand in defiance of unconstitutional laws
    do so out of duty, honor, oath and love of country.


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