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Jeep Yj 4cyl. Weird Lurching When Crawling In 4lo

Discussion in 'Quitters' Club' started by DanStew, Jul 26, 2020.

  1. Jul 26, 2020
    DanStew

    DanStew Preowned Merkin salesman Staff Member

    Lexington, South...
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    Sep 22, 2002
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    4,585
    I was at Uwharrie this past weekend wheeling and i had an odd experience with my jeep.
    I was in 4lo and between 2nd and 3rd gears most of the time on rocky trails with small fields of football sized rocks. It felt like the jeep was lurching (not sure about what else to call it) when crawling. Like it needed more fuel. it was pretty uncomfortable and literally seemed to be beating me up because the jeep just didnt seem to be crawling smooth. i have had this happen before, and it seemed like i had to settle down the motor be releasing the throttle. But this time it just seemed to happen all of the time. The jeep drives just fine in 2wd, no lurching. It is difficult for me to put the lurching into words. But think about if you have warped front rotors of your vehicle and when you are slowing down you feel the vehicle "lurch" when you get pssed the warped spot in the rotor. Pretty much how i cna describe what i am feeling. I have not changed anything on the Jeep, i have been running 35s and 4.88 gears for the last 4/5 years. just seemed like this time it just annoyed me more and felt like i had to release the throttle more to settle the lurching down.

    Has anyone else experienced this? The jeep ran flawlessly otherwise during the weekend, just the little rocky portions that seemed to be the cause to the problem. The jeep may have needed more fuel for the motor, but at the speed i couldnt go any faster without baja'ing and destroying the jeep.
     
    DanStew, Jul 26, 2020
    #1
  2. Jul 26, 2020
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    Out of phase front driveshaft?
     
    Fireball, Jul 26, 2020
    #2
  3. Jul 26, 2020
    73 cj5

    73 cj5 Not ready for the junkyard yet

    Clinton, Mississippi
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    Jan 10, 2014
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    2,143
    I have in a couple different vehicles but I figured it was slop in the powertrain. :shrug:
     
    73 cj5, Jul 26, 2020
    #3
  4. Jul 26, 2020
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Spokane Valley, WA
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    Aug 13, 2015
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    My first thought was fuel pump. How much fuel was in the tank when it was happening? Can you hook up a fuel pressure gauge?
     
    ITLKSEZ, Jul 26, 2020
    #4
  5. Jul 26, 2020
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    Aug 3, 2003
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    "Rocky trails..." Only in 4-wheel? "Just the rocky portions..."

    Drivetrain wrap-up because the tires aren't able to slip and equalize. Then they do. Repeat.
    Like 4x4 on pavement, same thing.

    You have a lifted suspension? My YJ got noticeably smoother with a slip-joint-eliminator (SYE) kit, which includes a dual cardan UJ.

    EDIT - Slip YOKE eliminator.
     
    Last edited: Jul 27, 2020
    PeteL, Jul 26, 2020
    #5
  6. Jul 27, 2020
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Sep 23, 2002
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    I agree with PeteL. Probably more noticeable now that the springs are well worn in. The drivetrain and springs load up then when things get a little easier they unload causing the Jeep to lurch. Mine does it and every Jeep I’ve watched in rocks with a supple suspension has done it.
     
    nickmil, Jul 27, 2020
    #6
  7. Jul 27, 2020
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    12,529
    SYE= Slip Yoke Eliminator
    For clarification.
     
    nickmil, Jul 27, 2020
    #7
  8. Jul 27, 2020
    DanStew

    DanStew Preowned Merkin salesman Staff Member

    Lexington, South...
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    OK. if it something that is kind of normal, then i wont stress that much. I was thinking possibly it was because i did not air down enough to maybe give a bit more give. It is lifted, it has the SYE. I did lie, i did a mod before this, i added a spartan locker to the rear axle last december before my last uwharrie trip, but did not end up going because i threw my back out :(
    I just seemed to be a bit more annoying this trip out.
     
    DanStew, Jul 27, 2020
    #8
  9. Jul 27, 2020
    Lockman

    Lockman OK.....Now I Get It . 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Silver Hill,...
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    3rd Gear in 4 Lo would cause that too ? , IME
     
    Lockman, Jul 27, 2020
    #9
  10. Aug 25, 2020
    OnlyOneDR

    OnlyOneDR Member 2023 Sponsor

    R
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    Mar 4, 2020
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    Lunchbox lockers like the Spartan introduce more drivetrain slack. Wheeling on rocks with all four wheels under power stresses the drivetrain on a part-time 4x4 to where the front and rear drivelines do not cover the same amount of ground (rotating different amounts to traverse terrain) so the binding that ensues has to relieve itself somewhere and that usually means tires that skip and hop a bit as well as torquing the axles to where u-joints and other components cannot turn as smoothly as when on flat ground, especially in 2wd where there is little to bind up. If I assume that your YJ still has the NP231 transfer case then you may also have some chain stretch for the front output meaning that it will not run smoothly either.

    My Nissan and my Blazer both have mechanical rear lockers (Nissan is a Detroit, Blazer is a Lock-Right) and you eventually get used to the quirks of having them. Turning tight parking lot circles on pavement is always entertaining.
     
    OnlyOneDR, Aug 25, 2020
    #10
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