OK guys I need some advice. I currently have a YJ with an approx 5 1/2 to 6" SOA lift. (I am unsure as how to accurately measure a lift, this is my first Jeep) The shackles are about 6 1/2 " bolt to bolt. I believe the axles springs are stock AND FLAT. I am wanting to swap out both shackles and springs. I want to install roughly 1 or 1 1/2 " lift shackles( I understand these are approx 6" bolt to bolt when it is a 1" lift, per quadratec website).
What amount of lift should my springs have, 0", 1" 2" 3". I AM RUNNING 38" MT'S so I need to keep the height to fit the tires. I underdstand this is a SOA so there is already added lift with the reposition of the springs over the axle. So any help is greatly appreciated.
Thx EVERYONE  

id be careful about using lift shackles... theyll throw off your caster so keep it to a minimum. im running 1 inch shackles and dont really care fo how it effects my steering, beware...  

I'm not sure what your question is.

A YJ SOA with stock springs will net you a 5.5" lift.

What are you trying to accomplish? Do you need more lift, and you're trying to do that with shackles?

Or, are you trying to get rid of some assummed lift shackles and replace them and the springs to get the same lift as you have now, only with all spring and no shackle for the lift?  

so, yer looking for about 6" lift springs (sua?) or 2" lift springs soa and go back to stock length shackles.
sounds like the shackles you have could be reused beings they are 1- 1 1/2" longer than stock.

thats gotta be tight with 38's under a 6" on the YJ?  

Ok let me try to clarify, the previous owner said that it has an approx 6" SOA lift. It also has a 2" body lift. I would like to keep the same amount of lift by replacing the axles( cuz they are severely flat and in fact the front driver has a slight reverse bend) and maybe use a shorter shackle( preferrably a 1" lift shackle). My guess is that I measure from bottom of axle to top of spring sitting on the axle and that will give me the amount of lift with a stock axle. I don't like these shackles as they are without mid shackle suppport. My quandry is in replacing the spring with say a 1" lift shackle, what amount of lift on the spring would keep me at approx the same amount of total suspension lift. I have found 0", 1" and 2" lift leaf springs that give a certain amount of lift when placed SOA design. Thx Hope this makes it clearer than mud.  

stock replacements should do the trick then,  

If you measure the thickness of the spring pack and add that to the axle tube diameter, that is the difference between SOA vs. SUA.

On a YJ the stock spring pack is 2" and the axle tube diameter is 3.5". That is where the 5.5" comes from.

So with that you should be able to figure out what you want.

As far as shackles are concerned, there is more than meets the eye. Generally the length of the shackle works in conjunction with the physical characteristics of the spring. Changing the length changes the spring performance.

Also, the angle of the shackles are important. A longer shackle changes the angle of the shackle which can lead to problems.

Shackles that have no mid support are not bad. They actually articulate better for off-road. The mid support helps tighten up the suspension on-road, but with 6" of lift and big floatty tires, it's not going to be a difference you'll notice.

Boomerang shackles were invented for YJs. Their shape helps with clearance issues. Also, their mid support keeps them from inverting, because the mid support hits the frame to stop the shackle from flipping over.

Click here for more info on shackles.