2012 JKU pinion/caster - JeepForum.com
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post #1 of 3 Old 07-28-2021, 08:03 PM Thread Starter
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1994 YJ Wrangler 
Join Date: May 2014
Location: unionville
Posts: 40
2012 JKU pinion/caster

Looking for some help with figuring out what my steering wheel shake is.

I just recently installed a OME 2.5 inch lift with 1 inch spacers front and back. Also installed some OME shocks. A JKS adjustable trackbar, a new steering stabilizer and upper/lower control arm bracket. Also installed new adjustable sway bar links. When driving I get a shake/wobble in the steering wheel at 50 and above. I did not have this before I did the lift.

I have gone over the torque specs and they are at OEM specs. I can not move my tires from 12 to 6 or 3 to 9 so I believe my tie-rods and ball joints are good. Where should I start?

This got me thinking about Caster and pinion angle... Although with pinion angle, I don't believe I would have a problem with the steering wheel shaking.. But I COULD if the Caster isnt right... Well.. I think I am the only person that owns a JKU that cant measure... I have attached some pics for you all to look at and help me. Which I say thank you now for the help.

My caster angle is around 12ish. Due to this number I should have 6 degrees of difference at the pinion angle and a measurement of 6.......BUT I DON'T!!!!
My Pinion angle is around 0. ( I have a stock Dana 30 front axle that came with the JKU )

My understanding of this is that this measurement is impossible.... Right? If there is a 6 degree difference how the hell do I have a 10ish degree difference???? Is my stuff in that bad of a bind?
If I make the upper arms longer will that increase caster or does it stay the same at 12?
I just went out and tested the angle of my Lower control arm and its at zero degrees.

I have not had an alignment yet.. I wanted to make sure I tried everything I could before I went over for an alignment.

What is the stock length of the JKU from the inside top of the front shock tower to the center of the bottom of the shock? I am at 21.

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IMG_1646.jpg   IMG_1647.jpg   IMG_1648.jpg   IMG_1649.jpg   IMG_1651.jpg  


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2012 Jeep JK unlimited
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post #2 of 3 Old 07-29-2021, 12:00 AM
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2008 JK Wrangler 
Join Date: Jan 2009
Location: Maine
Posts: 5,269
Check lower ball joints for up and down play. The 12/6 and3/9 thing won't check that.
Putting the angle finder on top of the pinion flange isn't as accurate as putting it on the front or rear face of the flange, assuming the Jeep is sitting on a level surface.
Where your angle finder reads 12 or 13 appears to be set up for camber. That should be measured by putting a straight edge on the wheel and reading that with your angle finder, assuming the Jeep is sitting on a level surface.

Get an alignment check. You can't get an accurate caster reading with an angle finder at home.
Once you know your true caster, you can keep track of how much you change it with your angle finder at home.

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post #3 of 3 Old 08-13-2021, 10:53 AM
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2012 JK Wrangler 
Join Date: Sep 2011
Location: Lake Havasu City
Posts: 10,283
2.5 will not change caster all that much and they way you are using that tool looks to be for camber. Caster is the dial facing tire or body. I would use a phone app that is free for this over that as well.

if camber is off meaning tires lean out or in you may have a bent axle C. That tends take some hitting something hard. if its less then a few degrees adjustable ball joints can be use.

caster jk is rather wide so over 4.5+ no more then say 7. But at 2.5 stock drive shafts.....You have a shimmy its tire generally. unless something is worn.

place a socket over the BJ to get a better flat spot.

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