RRO OME yj conversion...start with axle shims?

[Techlight]

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. The lift 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.

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 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?

Any advice is appreciated. Thanks.

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[mriplaybass]

Both are important. You can check your caster angle by getting an inexpensive angle gauge from one of the building centers, or you can even download an app to your phone that will get you pretty close. Just measure on a known flat surface such as across the pinion yoke with the drive shaft removed, across 2 of the diff cover bolts, etc. You will only know which shims to get by measuring, not by trying to figure things out based on how much lift you expect to get. I did a 4" Rubicon Express YJ conversion last year and wound up having to make a few choices. If I kept my caster angle correct, (I had mine around +7°), the driveshaft U joint at the transfer case bound up. If I shimmed the axle to eliminate the bind, I ended up with only +2° of caster which made things pretty squirlly on the highway. I temporarily used an offset U joint to correct the problem, but I really couldn't drive much over 20mph without causing a lot of vibration. I am currently rotating the C knuckles on the axle to allow me to get correct angles on everything without the need for an offset U joint. I should mention that my cross member is considerably higher than a stock one, so you probably will not encounter this problem.
The main thing to know is, your transfer case angle needs to match your diff pinion angle within a degree or so. In other words, the driveshaft should be near parallel to the 2 yokes. There are lots of ways to get them within tolerances, but you won't know until you install things and measure the angles.

 

[Techlight]

Fun times then ...I'll throw everything in I guess and figure it out after. I was thinking of picking up one of those angle finders from the hardware store anyway just to get a rough idea where I was after I was done without having to take it to an alignment shop. At least then it won't be as much of a surprise when they tell me how far I'm off haha. Hopefully everything will be close enough without needing too many adjustments.

I know I'm being a whiner but I really don't want to install it and then drop it to add shims. Nature of the beast though I suppose. Either way I'm sure I'll just be excited to not be on the stock springs anymore. This is my third Jeep and the CJ springs are killing me. My 60 stock Willy's CJ5 rode way better than this thing and those springs were tired too.

Thanks for the reply.

 

[mriplaybass]

Ya, welcome to the addiction! Any time you change just one thing on these CJ's, it affects several other things somewhere else. I just came in from my shop to decompress for awhile. I put my axle in to make sure that I have all the correct angles before I weld in the C knuckles, and discovered that the driveshaft that just made last year is too long! More work!

Just an FYI, when you do your measurements, make sure that you do them with the suspension loaded. Good luck!