Re: OME worth the $$$ ?
You might not have to have the spring perches relocated. In my case, for some reason, an offshelf 6- or 8-degree shim was not enough to rotate the rear axle upward to bring the pinion in line with the rear CV driveshaft. Most people who install the SYE & CV rear drive shaft do not have to go to such extremes. My theory is that, due to manufacturing tolerances, my spring perches were located such that the pinion was rotated down more than normal to begin with, so it needed greater correction when modifying the driveline.
The perch is located in the same position left to right, but in a different position front to back around the axis of the axle. Hope this makes sense. No lift is lost, because the axle remains in the same location relative to the springs and chassis. It just points the pinion up a little higher.
The JKS adjustable track bar is for the front. Maybe someone else makes one for the rear. You've probably read an article on this setup in one of the 4x4 magazines awhile back where it was mistakently installed on the rear of a YJ. In a subsequent issue, the same magazine printed a followup article correcting this issue. Locating the track bar in the front, like it's supposed to be, actually improved articulation a little, according to the followup article. Companies other than JKS may make an adjustable rear track bar, but I hear that they contact the frame at some attitudes, but don't quote me.
The Currie SYE kit is around $300-400, and the rear CV drive shaft is extra. I paid about $700 to have the Currie SYE and rear CV drive shaft installed on my YJ.
JB Enterprises makes a SYE kit that is supposed to be stronger, as does Advance Adapters. They are more expensive by about $200-300, though. I've had no problem with my Currie one, though.
I think soneone (Rubicon Express) makes a SYE that's even less expensive, but you have to modify your transfer case output shaft yourself, and I'm not skilled enough to undertake this risky modification myself, and I don't trust any of the 4x4 shop here on Phoenix to do it. So I went for the Currie kit.
If you do the SYE, you will no longer need the transfer case drop kit, which is an advantage, because you get back about 5/8" clearance that you lost by dropping the transfer case in the first place. If you install the SYE and achieve the optimum rear pinion angle by either shimming or modifying the spring perches, there's no reason to use the transfer case drop kit. I personally believe that dropping the transfer case is a kluge which stresses the motor and transmission mounts and aggravates the front driveline U-jount angles. But it's a cheap alternative to the SYE, if it works.
The degree shims, which come with the OME rear springs may or may not be needed, based on your individual YJ's peculiarities. OME, like other lift manufacturers who provide shims (not all do), provide the shims of a degree that seemed to them to work for most YJ's.
By using the drop kit and degrees shims provided by OME, you may have no vibration, and it may work fine. But if it dosn't, you'll have to tolerate the vibration or spend more money.
I still have the stock shackles, with OME bushings. The stock shackles are fine, but I'm not a hard-core rock crawler. Other shackles may be of a different length than stock, which will affect the steering geometry and hard handling to a degree. I've been tempted to get some greasable stock length shackles, but it's not a priority right now.