Is this axle too far forward? - JeepForum.com
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post #1 of 19 Old 02-24-2020, 07:37 PM Thread Starter
nick613
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Is this axle too far forward?

I feel like this might be a stupid thing to ask but Im driving myself nuts with all these adjustments with my pieced together lift! I think I've found a decent caster angle and pinion angle compromise here and think I'm good for tire clearance if I adjust the charcoal canister a bit just incase.

Whats everyone's opinion here? Its lifted 4.5 inches and has control arm drop brackets with IRO adjustable control arms. I think the driveshaft is ok lengthwise but if not I have one about an inch longer that should be ok.

Thanks!

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post #2 of 19 Old 02-24-2020, 08:43 PM
Timo_90xj
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With drop brackets I think you should be fine, axle shift at full compression should not cause you issues with coil bind or axle shifting forward too much. However, that depends on your control arm geometry, so a picture showing front CA angles would help. If CAs are almost horizontal, you should be fine.

How do your coils look like? About straight, not bowing?

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post #3 of 19 Old 02-25-2020, 04:29 AM Thread Starter
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I'll pull off the wheel and get a good pic of the coil and control arm angles this evening. The coil has very little bow in it and the control arms are just about flat

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post #4 of 19 Old 02-25-2020, 06:22 PM Thread Starter
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Heres a pic showing the control arms and caster. Also included a pic to show the driveshaft angle. Does that look ok? How can you tell if the driveshaft is too short? I have a slightly longer one that I'll probably switch to but its from the junkyard so I trust the u joints in my current one more. They are both double cardan shafts.

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post #5 of 19 Old 02-25-2020, 10:08 PM
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Axle location and coil looks good to me and the CAs being almost horizontal uptravel will result in the axle shifting a little towards the rear at full compression, so I wouldn't change axle location at all.

However, your pinion angle is way off - with the double cardan joint @ the TC, angle at the pinion should be very close to zero. Slightly shorten your lower CAs and lengthen UCAs for better pinion angle.
Have you checked your caster angle? Preferably it should be around 6 +/- 0.5, but on a lifted Jeep you often end up with less than that when balancing between non-vibrating front DS (pinion angle) and caster angle.

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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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post #6 of 19 Old 02-26-2020, 08:08 AM Thread Starter
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Ok thanks for the advise. Whats the best way to check caster angle? I have an angle finder now just not sure where to put it. I guess I'd be shooting for about 4.5 or 5 degrees to be around a happy compromise?

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post #7 of 19 Old 02-26-2020, 08:24 AM
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I'm also doing a Frankenstein lift with Rubicon Express RE1345 coils and Super ride lower control arms. That picture Nick posted and the simple explanation that Timo posted sure helped!

Nick, flat spot under lower balljoint on C.

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post #8 of 19 Old 02-26-2020, 08:47 AM
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Originally Posted by nick613 View Post
Ok thanks for the advise. Whats the best way to check caster angle? I have an angle finder now just not sure where to put it. I guess I'd be shooting for about 4.5 or 5 degrees to be around a happy compromise?

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I use the top of the upper balljoint, seems to work well enough.


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post #9 of 19 Old 02-27-2020, 04:21 AM Thread Starter
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Looks like Im currently at about 10 degrees of caster... Guess my eyeball angle finder was off lol

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post #10 of 19 Old 02-27-2020, 05:52 AM
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Wow.. That explains the horrific pinion angle. Start with about 6 of caster, then check pinion angle and go for a test drive. If no vibes, you're good to go. If you habe vibes, go to something like 5 and re-adjust if still having issues.

By then you have realized why double- adjustable CAs are so damn good for suspension fine-tuning

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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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post #11 of 19 Old 02-27-2020, 06:55 PM Thread Starter
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So here it is sitting at about 5-5.5 degrees, my angle finder reads 6.5 but the jeep is sitting a bit out of level so Im accounting for that. Pinion angle looks great but not sure about the bow in the springs.

Also I have my stab bar end links rubbing on the spring on one side. It isnt quite touching at ride height but rubs as it articulates... Im thinking I might just take the cut off wheel to that bracket and see if I can take off enough material

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post #12 of 19 Old 02-27-2020, 07:45 PM Thread Starter
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Maybe I should push all 4 arms forward about 1/2" or so? Maybe more? I pulled in my lowers 1/2 and pushed out my uppers about 3/4 to get it where it is now.

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post #13 of 19 Old 02-28-2020, 12:53 AM
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You might check clearances with the steering full left and full right. You can get a hefty buddy or two to put their weight on the left end of the front bumper and then the right end of the front bumper with the sway bar disconnected to check the clearance with the front springs compressed. Ideally, you want to be against the bump stops.

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post #14 of 19 Old 02-28-2020, 10:57 AM
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Maybe I should push all 4 arms forward about 1/2" or so? Maybe more? I pulled in my lowers 1/2 and pushed out my uppers about 3/4 to get it where it is now.
With the coils bowing now that you corrected the pinion- and caster angles, you may need to pull the axle back a little - just enough to prevent the swaybar from contacting coils.


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Originally Posted by AlamoJeeper View Post
You might check clearances with the steering full left and full right. You can get a hefty buddy or two to put their weight on the left end of the front bumper and then the right end of the front bumper with the sway bar disconnected to check the clearance with the front springs compressed. Ideally, you want to be against the bump stops.
There is no human force to push the coils in all the way, they have about 190-240 lbs/in coil rate depending on the coils. Compressing a coil 10" would already require 1900-2400lbs. of force., and 5" would be half of that.
The best way to go through the full travel range* is to pull the coils and swaybar endlinks, then bolt the tires on, and test thoroughly. Jumping on one corner even if you can bottom out that corner is nowhere near full flex, so it really shows nothing.

* Straight up- and downtravel, full flex both ways with the tires straight and at full lock both ways

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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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post #15 of 19 Old 02-28-2020, 11:03 AM
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As an example, this is from last summer when I tried flexing the Jeep on the driveway; this was nowhere near full flex in the front - swaybar disconnected.
Good luck trying to achieve full articulation with a couple buddies jumping on the front fender


1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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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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