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Thread: Pinion angle

  1. #1
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    Default Pinion angle

    I have owned my Jk for 8 odd years now, bought with a 3.5 inc Rubicon express lift and 35 inc tires . I then added a Teraflex leveling kit . This added another inc of lift . From day one I had this "harmonic" vibration , more noticeable when going over 130 odd . Always thought it was tires . hard to explain the noise , but it was their . I have always had a stock rear drive shaft, so I thought that part of the drive train is sorted . After destroying prop no 3 on Carnage canyon I had one made up to my own design . As the cvs on both side were fine , i asked Mr Propshaft to build me a shaft to connect the two cv's with a slip joint in the tube. Job was done and I thought this was a cool idea.
    the vibration was still there but after many years of driving I was used to it , kept me from going over 130 . Then at a jeep club meeting I took a member for s spin, His immediate comment was that my driveshaft is not lekker or that the pinion angle was not set correctly. Told him that the noise has always been their , and apart for my modified prop nothing has ever been changed as long as I have owned the JK .Once stopped he had a look and said I shoub rotate the diff up to get a better pinion angle , he was sure that it would get rids of the vibration.
    Decided that nothing ventured nothing gained , on the to do list . But it meant I had to remove the control arm to adjust them . quite a job but doable , at my shop I got in under the jeep to check things out and found that the slip yoke had lots of play on it , Had a chat with DVR and it was decided that I need to take the prop out and take it to him to have it inspected . At Dirks workshop we decided that my idea was cool but the slip yoke used was to thin and not up to the job , and also using two cv joints not a great idea. To many welds needed to fit the bottom cv to the tubes. decided to make a new driveshaft with 3.5 ton slip yoke . Nice job , got the shaft back , installed it , took it for s drive and low and behold the harmonic vibration was still there . so it had to be pinion angle .
    Jeep back to my shop , out with the control arms make them longer . refit , test ride and all sounds ok . On the highway , the vibration is still there , but not bad . So last week I decide to bring the jeep back to my shop for some more tweaking, remove arm again , make them 1/2 turn longer , ( in the meantime I downloaded a angle finder app) took some measurements , and found that the yoke and shaft is just about 100% lined up, within 18/2 degree . tightened up everything and over the weekend took the jeep out on the highway , no harmonic vibration . runs smooth. Sometimes it take a while to get things sorted, never to late and it can be done
    Last edited by NEON DEON; 2018/07/23 at 01:25 PM.
    05 TJ SAHARA
    08 3.8 JK ULTD RUBICON

  2. #2
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    Default Re: Pinion angle

    Shaft?

    Just remember the more yo rotate the diff up, the more caster you lose as well. So you gotta find a balance between the 2.
    Stu.
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  3. #3
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    Default Re: Pinion angle

    Quote Originally Posted by roadhawg View Post
    Shaft?

    Just remember the more yo rotate the diff up, the more caster you lose as well. So you gotta find a balance between the 2.
    ja let's swop a small vibration for a major death wobble.........
    Jakes Louw
    2012 Jeep Sahara Unlimited 3.6 V6
    Percivamus

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    Default Re: Pinion angle

    JELO , please explain how one gets death wobble from tilting the rear diff pinion angle up ? Some guys comment just to comment , did not read the post properly , but have to chirp .
    05 TJ SAHARA
    08 3.8 JK ULTD RUBICON

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  6. #5
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    Default Re: Pinion angle

    Quote Originally Posted by NEON DEON View Post
    JELO , please explain how one gets death wobble from tilting the rear diff pinion angle up ? Some guys comment just to comment , did not read the post properly , but have to chirp .
    Is the dreaded wobbly not restricted to the front only, and very sensitive to front suspension changes?

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    Default Re: Pinion angle

    Quote Originally Posted by NEON DEON View Post
    JELO , please explain how one gets death wobble from tilting the rear diff pinion angle up ? Some guys comment just to comment , did not read the post properly , but have to chirp .
    sorry, you didn't have much punctuation or sentence construction so I didn't spot the rear axle portion, it wasn't that clear

    So I'll take this one, fair comment "did not read the post properly "
    Jakes Louw
    2012 Jeep Sahara Unlimited 3.6 V6
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  8. #7
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    Default Re: Pinion angle

    All ok , just yanking your chain @ JELO
    05 TJ SAHARA
    08 3.8 JK ULTD RUBICON

  9. #8
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    Default Re: Pinion angle

    Quote Originally Posted by Dirk View Post
    Is the dreaded wobbly not restricted to the front only, and very sensitive to front suspension changes?
    yes, I didn't read, he got me fair & square
    Jakes Louw
    2012 Jeep Sahara Unlimited 3.6 V6
    Percivamus

  10. #9
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    Default Re: Pinion angle

    Deon I have posted it somewhere here on the forum. The rear Dana 60 on my Yank Ranger is around 10deg. Perfect inline with the rear prop. We have done the same on the Little G60 Patrol no ill effects.

  11. #10
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    Default Re: Pinion angle

    I also thought it was the front actually.


    My bad.


    But yes, angling the (front)diff up makes you lose caster and you get more picknpay trolley wheelie as you lose more caster
    Stu.
    Current:
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    NO LOCKER NEEDED!!!
    KTM 1190 Adventure

  12. #11
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    Default Re: Pinion angle

    Deon, you've just confirmed a problem that I have bee battling with for years now. I've got the 3.6 JKU and a 2.5 AEV lift. Standard size wheels +-

    My vibration sets in between 95 and up to 105, and I've had a few diagnostics from reputable aftermarket dealers and Jeep workshops. They all point to the front propshaft and say the slip joint is a little loose and I should replace the whole propshaft.

    However, a little while I changed to a Teraflex 2.5 lift (thought the AEV was too hard). This was a level setup and guess what......vibration gone.

    Since then the AEV 2.5 is back as I tow a caravan and the Teraflex is just not hard enough. Back to a "bum-up-stance" and the vibe is back. So now I must measure and correct the rear pinion angle. Do you have the figures? Angle?

    Did you fit adjustable rear control arms?
    Ubbo
    2011 FJ Cruiser
    2014 Rubicon - Sold

  13. #12
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    Default Re: Pinion angle

    In order to tilt the diff you will have to have adjustable control arms , if not fitted then I dont think one can do the job , I dont have measurements , but downloaded a angle finder to my phone and that helped , final angle was around 10 degrees .
    That said I do think the front prop can ad to vibrations , I am goin to remove mine and fit a larger diameter slip yoke , and service all the joints at the same time .
    05 TJ SAHARA
    08 3.8 JK ULTD RUBICON

  14. #13
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    Default Re: Pinion angle

    Quote Originally Posted by NEON DEON View Post
    In order to tilt the diff you will have to have adjustable control arms , if not fitted then I dont think one can do the job , I dont have measurements , but downloaded a angle finder to my phone and that helped , final angle was around 10 degrees .
    That said I do think the front prop can ad to vibrations , I am goin to remove mine and fit a larger diameter slip yoke , and service all the joints at the same time .
    Thanks. I've just costed a full set of Alpine adjustable and rebuildable control arms. R23k. Not too bad but still a lot of cash.

    But probably worth it in the long run. My Rubi is going to have to last me another 10yrs as a holiday car - really can't justify spending R800k and more on a new JL

    I'm pretty sure the vibration is caused by the caster of the diffs, and most likely the rear as I set the front to the correct angle.
    Ubbo
    2011 FJ Cruiser
    2014 Rubicon - Sold

  15. #14
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    Default Re: Pinion angle

    Quote Originally Posted by Ubbo View Post
    Thanks. I've just costed a full set of Alpine adjustable and rebuildable control arms. R23k. Not too bad but still a lot of cash.

    But probably worth it in the long run. My Rubi is going to have to last me another 10yrs as a holiday car - really can't justify spending R800k and more on a new JL

    I'm pretty sure the vibration is caused by the caster of the diffs, and most likely the rear as I set the front to the correct angle.
    Just get geometry correction brackets from AEV. Think it is about r2500 for the lot from Zone. For some reason the 2.5 AEV it is not included.
    2012 Jeep Rubicon Call of Duty MW3
    Synergy 3" lift
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  16. #15
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    Default Re: Pinion angle

    I've got the front and rear correction brackets, but the rear doesn't correct the pinion angle.

    After a little research I have determined that only the rear upper adjustable control arms are required to correct the pinion angle.

    The front Geo correction brackets work a treat. Got my caster to 5.5deg when I did the wheel alignment. Car feels stable
    Ubbo
    2011 FJ Cruiser
    2014 Rubicon - Sold

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    Default Re: Pinion angle

    Ubbo,

    I also have the 2.5 AEV lift in the JKU CRD, never had any problems and I tow, is this limited to the Rubi?
    Developed a Death Wobble in the front which we sorted after the kit had done 20k's!!!

    Jacques

  18. #17
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    Default Re: Pinion angle

    Jacques,

    I also had the CRD (2012) with the very same lift and never a problem or vibration - actually transferred it from the Sahara to the Rubi. Then had a death wobble/trolley wheel experience the day I drove Rubi home. Old Zone (Andrew) fitted the Geometry Correction brackets in the front and problem trolley wheel solved.

    The vibration remains though. it is slight and you need to be on smooth tar to notice and only between about 95 -105. No other speeds. Like I said in the OP it went away when I had the level coils in, which will change the rear pinion angle, but came back when I put the AEV coils back in.

    So I'm likely going to buy a set of upper rear control arms. (R7400)

    It vibrates when I'm unloaded or towing, no difference.
    Last edited by Ubbo; 2018/11/02 at 06:31 PM.
    Ubbo
    2011 FJ Cruiser
    2014 Rubicon - Sold

  19. #18
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    Default Re: Pinion angle

    Ubbo,

    Do you think there is a difference between the angles of the CRD and the Rubi? Had my kit also done by Andrew with all the correct brackets etc. Might be interesting maybe there is difference.


    Jacques

  20. #19
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    Default Re: Pinion angle

    This is interesting

    I have a 3 Synergy lift and no vibrations with brackets. Took brackets out and I battled with death wobble untill i replaced the control arms with adjustable. 1 of my buddies have aev 2.5 on his rubicon 4 door, no issues. Other has it on a 2 door rubi. we battled with death wobble and no vibrations. He fitted 35" tyres wobble disapeared.

    Why on some do we have issues and some not? I can understand on big lifts, but not on a 2.5.
    2012 Jeep Rubicon Call of Duty MW3
    Synergy 3" lift
    Metal Cloack Gamechanger Arms
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