Installed Iron Rock Rear UCA today.

Gman4q2 · Jul 20, 2024

So, as the tile says, installed the A-Arm this morning, everything went well. After droping it down it looks like my pinion angle is off a bit, no biggie since after i put everything back together FedEx showed up with my lowers, so I will adjust the angle when I swap out the lowers. My one question though is does anyone know if there is a spec on how many degrees of angle change you get with each revolution of the adjustable portion of the A-Arm?

Thanks

duderz7 · Jul 20, 2024

Unless you're doing some extreme lift you likely need to bottom out the upper control arm (short as possible) these were originally designed for a slightly longer vehicle. I'm also running the IRO uca but still running stock lower with about a 3.5 inch lift.

Gman4q2 · Jul 20, 2024

I am running about the same, 3.5 inch lift. OME springs front and rear with extra spring insulator(s). I also currently have the stock lowers on, but as I stated above I'll be swaping those out soon.

Dave_too · Jul 22, 2024

Running something similar along with IRO lower control arms and a 2 inch lift in the rear with HD shocks from OME. Matched everything as close as possible to the original Jeep setup it replaced. Back of the Jeep likes a little weight in it or it delivers a bit of a rough ride. This setup is about 2 years old. You may already be aware, but don't fool around with the control arm length; the suspension is designed to swing the rear wheels up on a curve towards the rear, rather than straight up and down.

WWDiesel · Jul 22, 2024

I am running the IronRock rear upper and lower adjustable control arms with IronMan Springs/Bilstein Shocks (2.5" lift).
Adjust lower control arms to get pinion angle to closely match transfer case output shaft angle as possible with vehicle setting on the ground with rear suspension loaded.
Slightly negative, 1-2 degrees down is good at rest with rear suspension loaded. That way when pinion is under load it tends to angle up slightly and will match output shaft angle.
Upper control arm Heim Joint adjustment bottomed out with large lock nut on the inside (backside) of the arm. I did cut ~1 inch off the end of the threads of the Heim/ball joint so it would NOT bottom out on the control arm when the adjustment was screwed all the way in.
Lower arms adjusted to ~1 inch longer than stock to place wheel/tire in center of the wheel opening.
See pictures/drawing

Gman4q2 · Jul 23, 2024

WWDiesel said:
I am running the IronRock rear upper and lower adjustable control arms with IronMan Springs/Bilstein Shocks (2.5" lift).
Adjust lower control arms to get pinion angle to closely match transfer case output shaft angle as possible with vehicle setting on the ground with rear suspension loaded.
Slightly negative, 1-2 degrees down is good at rest with rear suspension loaded. That way when pinion is under load it tends to angle up slightly and will match output shaft angle.
Upper control arm Heim Joint adjustment bottomed out with large lock nut on the inside (backside) of the arm. I did cut ~1 inch off the end of the threads of the Heim/ball joint so it would NOT bottom out on the control arm when the adjustment was screwed all the way in.
Lower arms adjusted to ~1 inch longer than stock to place wheel/tire in center of the wheel opening.
See pictures/drawing

Thanks. I'm thinking I'll have to lengthen my lowers also. I noticed my wheels are not sitting centered and the measurement is about 1-1/2" difference. I also hope that will fix my angle problem so I don't have to dig into the upper.

Dave_too · Jul 23, 2024

By Jeep-Chrysler's engineering design, the rear wheels are not centered and they are intended to swing up in an arc in reaction to a bump in the road rather than just jolt straight up. The ramifications with the pinon angle and its numerical significance are admittedly not clear to me. And whether matching pinon angles and how closely is a more significant thing to accomplish than re-engineering the way the rear wheels react to a bump, I've no clue. Go with God and please do accept my best wishes! Certainly let the rest of us know how things turn out a couple of years down the road. (We need better emojis for this forum.)

Gman4q2 · Jul 23, 2024

Dave_too said:
By Jeep-Chrysler's engineering design, the rear wheels are not centered and they are intended to swing up in an arc in reaction to a bump in the road rather than just jolt straight up. The ramifications with the pinon angle and its numerical significance are admittedly not clear to me. And whether matching pinon angles and how closely is a more significant thing to accomplish than re-engineering the way the rear wheels react to a bump, I've no clue. Go with God and please do accept my best wishes! Certainly let the rest of us know how things turn out a couple of years down the road. (We need better emojis for this forum.)

Thanks for the info. Just wondering if you had the measurement for your rear wheels, and also wondering if replacing the stock control arms might change that designed arc.

Dave_too · Jul 23, 2024

Give me a day or so. Jeep went in the shop yesterday afternoon as something has been chewing on the o2 sensor wires.

When I put this stuff in maybe 2 + years ago, I remember lining the old arms up with these while they were both off the Jeep. My initial inclination was to do as you're thinking (centering the wheel) and then I ran across the above info. Matched the lengths (new to old) before installing. I remember them being very close if not exactly the same.

Gman4q2 · Jul 23, 2024

Dave_too said:
Give me a day or so. Jeep went in the shop yesterday afternoon as something has been chewing on the o2 sensor wires.

When I put this stuff in maybe 2 + years ago, I remember lining the old arms up with these while they were both off the Jeep. My initial inclination was to do as you're thinking (centering the wheel) and then I ran across the above info. Matched the lengths (new to old) before installing. I remember them being very close if not exactly the same.

Do you remember where you got the info from? Or remember how much offset?

Gman4q2 · Jul 24, 2024

Well, installed lowers this morning, everything went as well as could go except had to purchase new sway bar bolts. Iron Rocks instructions are almost as bad as ther customer service response from thier web-site. I added 1/4" to the length and still have the pinion angle problem, so looks like i'll have to adjust the upper on my next day off. Maybe iron rock will get back to me by then with some answers to my questions like how many degrees of angle change you get with each revolution of the adjustable part of the UCA.

u2slow · Jul 24, 2024

Longer arms may help, but at some point you will need a longer driveshaft, or a driveshaft spacer. Basic right-angle triangle geometry.

I did the JBA tri-link extension years ago. It tilted the pinion up some. Nearly all the ujoint angle is at the tcase. I thought it would be a problem, and would need a CV style driveshaft... but that's not the case. It's been fine.

Gman4q2 · Jul 25, 2024

u2slow said:
Longer arms may help, but at some point you will need a longer driveshaft, or a driveshaft spacer. Basic right-angle triangle geometry.

I did the JBA tri-link extension years ago. It tilted the pinion up some. Nearly all the ujoint angle is at the tcase. I thought it would be a problem, and would need a CV style driveshaft... but that's not the case. It's been fine.

Yeah, I think the pinion angle is pitched down too much on mine. I have a digital angle finder so I'll check for certain. Whichever it is, when I took it for a spin after installing the lowers you could feel the vibration from the driveshaft, and I just replaced the U-joints a week ago so I know its not them.

Gman4q2 · Jul 29, 2024

by the way, anyone know the size wrench needed for the jamb nut?

Installed Iron Rock Rear UCA today.

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