Mopar LCA swap

DavidArmen

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It's possible they've changed something in the 2021s to get that caster up, maybe a slight difference in the LCA mounts perhaps???
They know low caster w/ Rubicons has been an issue and rather than giving them the proper LCA length maybe they've altered the mounts a bit to accommodate the old arms that apply to all JLs???

Otherwise maybe they might have to have a control arm recall for all pre 2021 Rubis???
I’m really not sure what or how they achieved this but I’d love to take more photos of certain parts for anyone who is curious. I was shocked to see a perfect 90 degree reading from one of the flat holes on the sides of the diff cover (I used the hole closer to the driver side).

I first thought they are using shorter upper control arms to bring caster back to 6ish degrees but I don’t think that’s very logical considering they wouldn’t even use currently extant longer arms they already make for their lift kits...





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blnewt

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I’m really not sure what or how they achieved this but I’d love to take more photos of certain parts for anyone who is curious. I was shocked to see a perfect 90 degree reading from one of the flat holes on the sides of the diff cover (I used the hole closer to the driver side).

I first thought they are using shorter upper control arms to bring caster back to 6ish degrees but I don’t think that’s very logical considering they wouldn’t even use currently extant longer arms they already make for their lift kits...
It's surely possible they could sneak a shorter UCA into the Rubi, would be interesting to jot the UCA part # down and see if it matches previous year Rubis :)
 

cbrenthus

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I'm thinking they changed the mounts for the LCAs on the axle. That would be a pretty easy switch and would only affect Rubicons - do any other Jeeps get the Rubicon front axle but without the suspension?
 

DavidArmen

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It's surely possible they could sneak a shorter UCA into the Rubi, would be interesting to jot the UCA part # down and see if it matches previous year Rubis :)
I’ll try to get a photo of the UCAs today and see if I can hunt down the location where the part number is stamped.
 

DavidArmen

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I'm thinking they changed the mounts for the LCAs on the axle. That would be a pretty easy switch and would only affect Rubicons - do any other Jeeps get the Rubicon front axle but without the suspension?
Good thought! I don’t think any other jeep trim gets the wide axles of the Rubicons but someone correct me if I’m mistaken.
 

pangmaster

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It's possible they've changed something in the 2021s to get that caster up, maybe a slight difference in the LCA mounts perhaps???
They know low caster w/ Rubicons has been an issue and rather than giving them the proper LCA length maybe they've altered the mounts a bit to accommodate the old arms that apply to all JLs???

Otherwise maybe they might have to have a control arm recall for all pre 2021 Rubis???
Hi all, I've been following this thread for some time and a few months ago I did the same thing. Got under the Jeep and tried measuring my caster with a magnetic angle finder.

I've always felt that I had pretty good steering, too, though there is some play. May end up trying to get the box replaced, but that's another story.

I was also surprised that my 2018 2-door Rubicon seemed to be showing me about 6 degrees of caster. I measured multiple times and always got pretty much a 90 degree angle on the front diff. This was before I made any changes to the suspension. Stock shocks, springs, control arms, etc. So maybe it's not something changed on 2021s that would explain this...

IMG_3437.jpeg


I have doubts about my measurements and before I saw these posts I shrugged it off to I don't know what I'm doing when it comes to measuring caster. :CWL: What I should have done is taken it in to get put up on the alignment rack and get real readings, but I didn't.

At any rate, I have since added 2" of lift and after that did get an alignment, and the caster was 3.9/4.3. I will be swapping LCAs with the longer Mopars soon, and will get another reading after that. But approximately how much should we expect caster angle to change from stock with 2" of lift without changing out any control arms? It seems that there are a lot of variables.

Just sharing my experience, and always trying to learn more!
 

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I have some concerns about when/how to tighten the LCA bolts/nuts:
If you tighten at fully extended position - the silent blocks will be at the stress in normal driving position and even higher stress at fully compressed position.
It looks that the best way to tighten is when car is at normal driving position (when resting on its suspension). This way it has to flex only half way (+-) during compression/decompression arm travel and should last longer due to lesser stress.

How did you tighten yours?
 
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DavidArmen

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I have some concerns about when to tighten the LCA bolts/nuts:
If you tighten at fully extended position - the silent blocks will be at the stress in normal driving position and even higher stress at fully compressed position.
It looks that the best way to tighten is when car is at normal driving position (when resting on its suspension). This way it has to flex only half way (+-) during compression/decompression arm travel and should last longer due to lesser stress.

How did you tighten yours?
Absolutely! The stock bushings do not have unlimited travel. They only travel one way about 30-45 degrees and the opposite way about the same amount. So it is extremely important to tighten steering and suspension bolts (upper and lower control arms, drag link, etc) when the Jeep is resting on the ground with its’ full weight. This way the suspension is at standard driving height and will be able to flex in and out in the proper amounts without over-stressing the rubber bushings.
 

blnewt

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Absolutely! The stock bushings do not have unlimited travel. They only travel one way about 30-45 degrees and the opposite way about the same amount. So it is extremely important to tighten steering and suspension bolts (upper and lower control arms, drag link, etc) when the Jeep is resting on the ground with its’ full weight. This way the suspension is at standard driving height and will be able to flex in and out in the proper amounts without over-stressing the rubber bushings.
Yep, this^^^ just torque them down to spec w/ the Jeep normally loaded on the suspension, that's why ramps work so well here as it keeps the suspension loaded and gives you room to get good leverage on the torque wrench & breaker bar.

But approximately how much should we expect caster angle to change from stock with 2" of lift without changing out any control arms? It seems that there are a lot of variables.

Just sharing my experience, and always trying to learn more!
It's roughly about 3/4 to 1 degree of caster for every inch of lift, so your 2" extra lift will decrease your caster about 1.5 to 2 degrees.

Since you have a Rubicon and a 2" additional lift you may want to look into adjustable LCAs as the longer Mopar LCAs may not be enough.
 

pangmaster

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It's roughly about 3/4 to 1 degree of caster for every inch of lift, so your 2" extra lift will decrease your caster about 1.5 to 2 degrees.

Since you have a Rubicon and a 2" additional lift you may want to look into adjustable LCAs as the longer Mopar LCAs may not be enough.
Thanks! Math checks out that maybe it really was close to 6 degrees stock. Hmmm... Maybe I got lucky!

Anyway, you are right about the LCAs. I bought the Mopars already because they were so damn cheap, but after trying those I may have to upgrade to adjustables. And then maybe I will just replace all the arms. It never ends...
 

FlashGordon

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Wow..what a driving difference. Took out on highway with 17mph wind and could easy steer with 1 hand on steering wheel and drastic improvement with the wandering. May have been combination of new steering box a few weeks ago as well as these mopar LCAs.

A few issues getting the LCAs after a few shipping/quality issues but just installed this morning. Great easy project with my 15 year old son and took us 2 hours taking our time. Breaking the bolts loose was tough but with impact and breaker bar we got it. Used 3.5" wood ramps to give more room under Jeep. Had to use floor jack for minimal adjustments to align bolts on new LCAs. Tourquing was a workout as 190lbs is tough..hardest was passenger frame side as tough to get angle and leverage.

Stock 2020 JLUR measurements at pumpkin was 4.5* pre-swap and 6.5* after. Consistent with measurement at knuckles showing 6.5*.

Thx again for everyone's advice and detailed installations.
20201018_144843.jpg
 

blnewt

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Wow..what a driving difference. Took out on highway with 17mph wind and could easy steer with 1 hand on steering wheel and drastic improvement with the wandering. May have been combination of new steering box a few weeks ago as well as these mopar LCAs.

A few issues getting the LCAs after a few shipping/quality issues but just installed this morning. Great easy project with my 15 year old son and took us 2 hours taking our time. Breaking the bolts loose was tough but with impact and breaker bar we got it. Used 3.5" wood ramps to give more room under Jeep. Had to use floor jack for minimal adjustments to align bolts on new LCAs. Tourquing was a workout as 190lbs is tough..hardest was passenger frame side as tough to get angle and leverage.

Stock JLUR measurements at pumpkin was 4.5* pre-swap and 6.5* after. Consistent with measurement at knuckles showing 6.5*.

Thx again for everyone's advice and detailed installations.
Awesome feedback there! Great to have your JL driving down the road without worry on your part. Our 2dr Sport w/ Rubicon lift, Longer Mopar LCAs, and the new cast iron steering box is now as perfect as I could have imagined prior to all of that. The new box seemed similar to the old aluminum unit until I racked up 1500 miles last week on a Vegas road trip. I think we had air in the steering lines that worked out of the system as it's so tight and true now, and that Caster at 6 is just right!
 

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