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Unread 11-09-2013, 11:42 AM   #1
rizz
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xj 3 inch lift upper adjustable control arm measurments

I am installing ironrockoffroad upper adjustable control arms. i have a 3 inch lift. when i spoke to one of the technical support members at ironrockoffroad they told me to set the upper adjustable control arms to 15 and a quarter inches. but the stock ones when i removed them are 15 inches. does a quarter of an inch make that much of a difference to adjust the caster angle? or should i set it a little higher say around 16?
ps. i am installing upper adjustable because i expereinced bad vibrations from my front driveshaft and it is defintely the caster angle

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Unread 11-09-2013, 01:06 PM   #2
biffgnar
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Set them at whatever angle makes your pinion correct and your handling satisfactory. For a front double cardan shaft the correct pinion orientation is inline with driveshaft. That can result in too low caster and handling issues. Then you have to experiment adding back caster slowly to see where you can get it to without driveline vibes starting back up. Manufacturers and people on the internet can recommend approximate settings but you are the one with your jeep in front of you. Trial and error at different settings often only way to get it right.
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Unread 11-09-2013, 02:08 PM   #3
Timo_90xj
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^- that exactly.

I do the initial setup by unbolting both uppers with all four tires on the ground, keeping a floor jack under the pinion to adjust for correct pinion/ caster angle. If the Jeep feels like crap to drive, readjust.
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Unread 11-10-2013, 01:40 PM   #4
sAe23
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Quote:
Originally Posted by rizz View Post
I am installing ironrockoffroad upper adjustable control arms. i have a 3 inch lift. when i spoke to one of the technical support members at ironrockoffroad they told me to set the upper adjustable control arms to 15 and a quarter inches. but the stock ones when i removed them are 15 inches. does a quarter of an inch make that much of a difference to adjust the caster angle? or should i set it a little higher say around 16?
ps. i am installing upper adjustable because i expereinced bad vibrations from my front driveshaft and it is defintely the caster angle
Caster doesn't cause vibration issues...

Not knowing what year XJ you have (and whether the D30 is low or high pinion), I would jump to the conclusion that at 3" of lift there shouldn't be any pinion angle issues

Did you bother to MEASURE your pinion and drive shaft angles before removing the stock arms?

And what IS (was) your caster angle??

At 3" your upper should be 15" (stock length) BUT you LOWERS need to be 16" (.25" longer)

Or, do as Biffgnar suggested
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Unread 11-10-2013, 01:59 PM   #5
Tom95YJ
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I'm running adjustable upper and lower arms at 3.5" of lift. Before I installed the adjustable arms I was running stock uppers and fixed lowers. My caster angle sucked now that I have all adjustable arms I have my caster dailed in and my suspension works much better on and offroad
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Unread 11-10-2013, 06:04 PM   #6
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its an 01 xj. sAe23-how do you go about measuring the pinion and drive shaft angles?
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Unread 11-10-2013, 06:35 PM   #7
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An angle finder from someplace like Harbor Freight ($10ish), or a plastic protractor with a weighted string attached to the middle.
Hold it flat against the drive shaft to read it.
For the pinion, there are a couple of ways.
One is to rotate the shaft so the pinion side of the U-joint is facing down and hold the angle finder against it (might need a socket to make a flat surface).
Another is to use the circular pads on either side of the diff cover.
Here are a couple of web sites that cover the issue:
http://www.4crawler.com/4x4/CheapTri...l#Introduction
http://www.4xshaft.com/techinfo.html (slopes vs angles and geometry 101)

You need to favor pinion angle over caster as too little caster might make it prone to wander (but you'll never need that little at 3"), but if the pinion angle is too far off you wear out U-joints and suffer vibrations.
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Unread 11-10-2013, 07:00 PM   #8
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thanks for the links, they look very informative, il read up on them before i start ripping off my control arms.
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Unread 11-10-2013, 07:10 PM   #9
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You can also set pinion using a tape measure. Rotate the axle so one of the crosses on the axle side u joint is straight up and down. Measure the distance from the cap on each of the top and the bottom to the axle yoke. If the top is less pinion is low, if bottom is less pinion is high, it they are equal they are inline. Doesn't give you an actual number but with most setups the actual numbers don't matter. It is just their relationship to one another that matters.
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Unread 11-14-2013, 11:26 AM   #10
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How do I rotate my axle? Should I use ratchet straps? Loosen my lower control arms also?
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Unread 11-14-2013, 11:28 AM   #11
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And should I have my front axle on jack stands or just keep em on tires
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Unread 11-14-2013, 12:06 PM   #12
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He was referring to the drive shaft. Just roll the Jeep until the yoke is verticle... Or buy the angle finder
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Unread 11-15-2013, 01:40 AM   #13
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Quote:
Originally Posted by rizz View Post
How do I rotate my axle? Should I use ratchet straps? Loosen my lower control arms also?
Place a floor jack under the pinion (on the housing, that is), and lower/ raise the pinion to achieve proper pinion and caster angles. Ratchet straps IMO are just a waste of time and energy when aligning an axle.

You can either keep the Jeep sitting on the ground, or place axle stands under the axle tubes as close to true height as possible and remove tires for easier access to bolts. No need to loosen LCA bolts, but it doesn't hurt either.

P.S. When unbolting UCAs and the weight of the Jeep on the front axle, make 100% sure (!!!) the pinion won't shoot upwards when removing the last bolt! In theory, it shouldn't do that, but anything is possible. If you feel uncomfortable, do only one UCA at a time. It's a bit of a pain that way - you need to go by a gut feel on the amount of adjustment required for the correct angles - so you may need to do it a couple of times. But it sure is safer that way. I've set-up my UCA lengths a couple times by fully removing both when the weight of the vehicle is on the axles and have had no problems. That doesn't mean something could happen though
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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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Unread 11-15-2013, 08:15 AM   #14
biffgnar
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Quote:
Originally Posted by Timo_90xj View Post
Place a floor jack under the pinion (on the housing, that is), and lower/ raise the pinion to achieve proper pinion and caster angles. Ratchet straps IMO are just a waste of time and energy when aligning an axle.

You can either keep the Jeep sitting on the ground, or place axle stands under the axle tubes as close to true height as possible and remove tires for easier access to bolts. No need to loosen LCA bolts, but it doesn't hurt either.

P.S. When unbolting UCAs and the weight of the Jeep on the front axle, make 100% sure (!!!) the pinion won't shoot upwards when removing the last bolt! In theory, it shouldn't do that, but anything is possible. If you feel uncomfortable, do only one UCA at a time. It's a bit of a pain that way - you need to go by a gut feel on the amount of adjustment required for the correct angles - so you may need to do it a couple of times. But it sure is safer that way. I've set-up my UCA lengths a couple times by fully removing both when the weight of the vehicle is on the axles and have had no problems. That doesn't mean something could happen though
This is great advice. I hate it when that pinion rotates up!

Another option is to look at some of the manufacturers that make double adjustable arms. You can crank them out to whatever length you need to get them bolted up. Then with both jam nuts loose you can move the pinion up and down just by turning the arms. They do cost a bit more so if you aren't going to be changing your pinion much single adjustable probably cool, but I've taken advantage of my double adjustables (on my TJ not my XJ) many times.
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Unread 11-18-2013, 04:04 PM   #15
rizz
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Hey so before I posted how to rotate my axle, i removed both UCA arms at the same time and the pinion shot up!!
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