As possible to 2 degrees lower than the angle of the drive shaft (ie: pinion=23 deg
drive shaft=25 deg). It will look as if the pinion is in a direct line with the drive shaft.
Click on any of the thumbnails below for a full sized image.
Spring Over Axle
Let me start by saying that this type of lift is not for the faint of heart. While this type of lift works well off road, it does have some disadvantages. For some people an SOA will go together and work right off the bat but in my case I am still tweaking my system. My problem has almost always been with the spring packs, they tend to wear out on me real quick. I can't count how many spring packs I have gone through, especially on the rear. Another problem that I have yet to completely correct is the shocks and finding the right setup that works. Once you go to an SOA you can't ask for shocks for a particular lift and have them work. In most cases you will have to make careful considerations as to which shocks to use and how long they need to be. For some setups your first guess will not work out like you had planned.
My setup
I am running kind of a strange setup. In the front I have a set of stock Wrangler springs with a Rancho full length 2" add-a-leaf for support. For shocks I am running a set of Doetsch Tech's . In the rear I am running a set Rancho 2.5" lift springs with Rancho full length and short add-a-leaves. For shocks I am running a set of Rancho RS9000's. A spring over is a big project so set aside a weekend (or more if you have never done one) to complete this project. Whatever you do take your time. Check and double check all of your measurements. Rushing through an SOA can definitely come back and bite you in the rear. Trust me on this one. Converting your YJ to an SOA with stock springs should net you about 5.5" of lift. Of course no one says that you have to use stock springs and you may have to experiment with different setups until you find the one that works for you.
Tips and parts
Like I said before it is very important to be as precise as possible with all of your measurements. CHECK AND RECHECK ALL MEASUREMENTS. This is probably the best tip that I can give you. Look here for a list of parts that I put together. Basically all you will be doing is relocating your springs to the top of your axles and lengthening the rest of the suspension and drive train components to accommodate the new lift. Probably the best way to do a spring over is to take your time and gather all of the parts before hand. You might be thinking "of course who is this idiot?". What I am referring to in particular is the SYE kit. I mention this because if you have already done the SOA and then you go to do the SYE kit it is a major project so you may as well do it all at the same time. This is a fairly expensive mod but it is worth the wait and will make the work easier in the long run. Do not be misled by people who say that this setup will not effect you on the road. It will effect your handling to a greater or lesser degree depending on how you set things up.
Matt Osburn has a really detailed write up on his SOA with lots of pics and a few links to other SOA sites.
Some measurements
Front perches: These need to be parallel with the old perches.
Rear perches: This is with the SYE installed. These should be set so that the pinion angle is as close
As possible to 2 degrees lower than the angle of the drive shaft (ie: pinion=23 deg
drive shaft=25 deg). It will look as if the pinion is in a direct line with the drive shaft.
Click on any of the thumbnails below for a full sized image.