RRO OME yj conversion...start with axle shims - JeepForum.com
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post #1 of 33 Old 02-10-2020, 08:05 PM Thread Starter
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RRO OME yj conversion...start with axle shims

Hi All

So I finally grabbed an OME conversion from RRO and I've been reading tons of install threads and generally gearing up for the install (yes I read the 75 page OME install page lol). The lift from Rocky Road Outfitters is supposed to be 3-3.5 total. They get 2.5 out of the springs and about a little over an inch with longer yj shackles front and rear. I don't technically want the shackle lift since I already have a 1" body lift and I only do mild'ish wheeling. But that's what it comes with and they didn't have stock yj shackles when I called. I figured I'll see what it's like and decide after.

My question is about shims to correct the caster. Should I install 4 degree shims from the beginning or install without and have it checked? Is it possible I wont need any with this lift or will I absolutely need some but noone knows what degree until its measured? I'm asking because in my head I figure that if most need them I might as well take a shot in the dark and possibly get lucky as opposed to not putting any in and having to take it apart. A 50/50 shot sounds better lol.

And additionally do I need to shim the rear axle the same or something less since I'm concerned about driveline angles instead of the more important caster on the front?


My rig is a 1984 Jeep CJ7 with a 1" body lift. I have a few other mods but nothing that "should" get in the way of the advice I'm asking for lol. I probably need to fill out some info on this forum. Usually I'm over at Jeep CJ forum but traffic is light on that site lately unfortunately.



Thanks in advance...I appreciate it.

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post #2 of 33 Old 02-10-2020, 08:19 PM
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I would not install any shims until you have the springs on for a while as they are going to sag a bit. You may find you don't need any at all.


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post #3 of 33 Old 02-10-2020, 08:30 PM Thread Starter
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Hey Jim!


...i guess it makes sense that your on this forum too lol...I was like oh hey a familiar handle! Thanks for the advice. I'm hoping I end up in the "I don't need shims after install" group. That would be nice. My caster is probably so screwed up right now with bent stock springs...I'm sure either way I'll be seriously happy with the new springs.
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post #4 of 33 Old 02-11-2020, 12:29 AM
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I usually donít disagree with Jim, but this case is the exception. I would install the shims, you will need them.

Matt
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post #5 of 33 Old 02-11-2020, 09:31 AM Thread Starter
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Matt...I appreciate the reply.

Hmmm...differing opinions is always fun. I know there's usually never easier answers with the Jeep, especially on this question. Any chance y'all would mind giving me the rationale for yes shims/no shims opinions? Not that I want anyone to be offended by the others answers. It's just that I've never tackled anything like this before and any extra details are helpful for me to make a decision one way or the other. Most of what I read online is usually yes or no you don't need them to begin with and of course different experiences with needing them or not. Seems so do and some don't.

Also if I was to install them what degree should I use? And should I only install them in the front.

Thanks again.
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post #6 of 33 Old 02-11-2020, 09:51 AM
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The reason the shims are necessary is because the YJ springs shift the front axle forward about 5/8", and the longer shackles rotate the axle, thereby reducing the caster angle. I started out with the 2 degree shims that came with my kit, which only gave me about 3-4 degrees of caster, and my CJ still wandered like a lost child. I then went with 4 degree shims and now I can let go of the steering wheel and my CJ will track straight as an arrow.

The vast majority of the guys who have done the YJ conversion have had to use 4-6 degree shims, to get their caster angle back to factory specs of 5-7 degrees.

The rear shims should also be used to correct the pinion angle, caused by the axle being further from the frame. That's why they are already installed on the rear springs in most kits.

Matt
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post #7 of 33 Old 02-11-2020, 10:27 AM
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The shims on the rear are different. Jeeps have short drive shafts. U-Joint angles increase quickly.
It is important that the u-joint angles are the same between the diff and the t-case.
If the angle is too steep because it's lifted so far away that you have to tilt the rear axle up to reduce the angle then you better drop the t-case so the angle matches.

So don't just think about tilting the rear axle without compensating at the t-case also.
Or better yet, running a double cardan and point the axle at the t-case.

On the front, yes, you probably will need them.
I have two positions on the front shackle about 1" apart and it changes the jeep from wondering to hand off driving.

It gets complicated fast doesn't it.
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post #8 of 33 Old 02-11-2020, 10:39 AM
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My reasoning is that until the springs settle you have no idea what degree shim you'll need. I like saving steps if I can and only doing the shim job once is my goal. It's your time and effort though and if you want to add them at the start you sure won't hurt anything in doing so. You may even hit it right the first time.

What other forum are we on together?


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post #9 of 33 Old 02-11-2020, 07:10 PM Thread Starter
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Hi All,

Thanks for taking the time to answer my questions and elaborate on your responses. I do appreciate that. I tend to try and think through all my installs and I haven't really messed with suspension on any of my rigs except for changing bushings all the way around. I always try to "not be that PO" lol.

I also called the RRO on the kit and asked them. They told me the majority of people installing the kit don't need the shims but that a few did (not that I can speak for the manufacture of course). They recommended installing it without and seeing where I was after. So I will go that route. They did say that the transfer case drop kit should be installed (I asked them cause I was curious and don't really like the look of the dropped skid plate with spacers). I guess I'll put it on though since they say it's not optional. Maybe later when I upgrade driveshafts I'll rethink that part of it.

Jim: How long do you think is enough time after install to "let it settle" and re-measure. I will of course measure the angles before and after install just to know where I am (not that it will matter because I have multiple bent springs and I'm sure my caster is affected to some degree...I was curious what is a good length of time/mileage to let the lift settle before attempting to adjust caster etc with shims (again if needed)?

Oh and I was referring ton jeep-cj.com by the way. I haven't been that active over there in a few but have way more posts than here for sure since this is like my 10th haha. I'm a supporter over there and I'll probably continue to be, but the traffic has seemed to drop off. I have noticed alot of questions go unanswered and I've had a few posts that plenty of views but no posts back. But either way that's where I recognized your handle from.
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post #10 of 33 Old 02-11-2020, 07:31 PM
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I had to drop my T-case to match the angles for the rear shaft.
I used some square tubing the length of the skidpan. Looked better that way.
Most people don't even notice I have one on there.


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post #11 of 33 Old 02-11-2020, 09:30 PM Thread Starter
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Quote:
Originally Posted by John Strenk View Post
I had to drop my T-case to match the angles for the rear shaft.

I used some square tubing the length of the skidpan. Looked better that way.

Most people don't even notice I have one on there.
I like the idea of the square tubing. Would definitely look more seameless. I dont like the look of the "pucks". I will install it cause that's what I got at the moment but will probably figure out something similar down the road if I can install something solid enough that matches the pucks thickness.



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post #12 of 33 Old 02-11-2020, 09:34 PM Thread Starter
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I like the idea of the square tubing. Would definitely look more seameless. I dont like the look of the "pucks". I will install it cause that's what I got at the moment but will probably figure out something similar down the road if I can install something solid enough that matches the pucks thickness.



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post #13 of 33 Old 02-11-2020, 09:36 PM Thread Starter
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Sorry for the double post. My phone isn't being my friend.

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post #14 of 33 Old 02-12-2020, 08:35 AM
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Quote:
Originally Posted by Techlight View Post
Hi All,

Thanks for taking the time to answer my questions and elaborate on your responses. I do appreciate that. I tend to try and think through all my installs and I haven't really messed with suspension on any of my rigs except for changing bushings all the way around. I always try to "not be that PO" lol.

I also called the RRO on the kit and asked them. They told me the majority of people installing the kit don't need the shims but that a few did (not that I can speak for the manufacture of course). They recommended installing it without and seeing where I was after. So I will go that route. They did say that the transfer case drop kit should be installed (I asked them cause I was curious and don't really like the look of the dropped skid plate with spacers). I guess I'll put it on though since they say it's not optional. Maybe later when I upgrade driveshafts I'll rethink that part of it.

Jim: How long do you think is enough time after install to "let it settle" and re-measure. I will of course measure the angles before and after install just to know where I am (not that it will matter because I have multiple bent springs and I'm sure my caster is affected to some degree...I was curious what is a good length of time/mileage to let the lift settle before attempting to adjust caster etc with shims (again if needed)?

Oh and I was referring ton jeep-cj.com by the way. I haven't been that active over there in a few but have way more posts than here for sure since this is like my 10th haha. I'm a supporter over there and I'll probably continue to be, but the traffic has seemed to drop off. I have noticed alot of questions go unanswered and I've had a few posts that plenty of views but no posts back. But either way that's where I recognized your handle from.
I haven't been on jeep-cj.com for some time, so long that I don't even remember when. I tend to use the same username everywhere as it's easier for me to remember.

Depending on how stiff those springs are as to how long it takes for them to get to the point of being broken in. The stiffer the longer it would seem.


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post #15 of 33 Old 04-15-2020, 04:54 PM Thread Starter
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Hi All,

So it's been a few since I put this lift on but I figured I'd update and ask a question.

I put the springs on without adding shims. Whatever was on there is what I installed. Had everything checked out and it was at 1.8 degrees caster. I spun the shims that were on there and ended up with 4.8 degrees caster. I'd like to get it closer to the 7.

Can I simply subtract these two numbers and determine that the shims that are on there are 3 degree shims?

What shim will get me to that magic number between 5-7? :To get my caster right do I need to remove the stock shims and add 5 or maybe 5.5 degree shims?

Thanks all in advance...I know barely anything about this and have never really messed with suspension before now.
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