The Rear ACOS for the ZJ Grand Cherokee has two separate components to it: The spring post extensions, and the ACOS itself:
Step 1) Install the Spring Post Extensions:
This one is pretty much a slam-dunk. All you need to do is slide them up and over the existing spring posts in the rear of the ZJ after removing the rear springs, and then keep gravity away from them. Your coil springs will exert absolutely zero sideways motion on them, so it’s a really simple and easy job. They can be affixed to the ZJ’s rear spring posts in the following manner:
1A) Remove the factory rubber spring isolators by sliding them down over the spring post. Keep them around somewhere out of the way, but you will not reuse them for this project.
1B) You can use Permatex, RTV, or any other sort of epoxy to hold them on. Clean both surfaces first, apply liberally, and hold them in position until the sealant congels.
1C) You can tack-weld them into position, but you’ll need to clean off the underbody coating in order to get the welder to get a good ground when the electrode touches the factory spring post as well as where the ground clamp it attached to.
1D) You can drill a small hole and insert a pan-head sheet metal screw, but the screw head may conflict with the spring wraps, depending on how tight they are at the top.
1E) You can take a 3-lb sledge hammer and hammer the end of the tubes *slightly* oval, and then hammer it into position up and over the spring post.
Step 2) Install the ACOS Spacers over the Spring Post Extensions:
Again, very simple and easy.
2A) Just slide the spacers up over the spring post extensions, so that the seat fully on the upper body, where the factory spring isolator would have been located, had you not removed it in Step 1A.
2B) Locate the “recessed” area of the upper ring, and make sure the recessed surface faces outward, so that it clears the pinch seam. The isolators you took off will give you a good indication of how the ACOS is to set.
2C) Tap the ACOS into position, or hold it with one hand and re-install the coil spring.
NOTE: There is no need to affix the ACOS to the spring post extension, because gravity will keep everything together. If you are jumping the Jeep (HIGHLY NOT RECOMMENDED, lol), make sure the shock length extended is not any longer than an inch from where the coil spring comes unseated. The ACOS will slide up and down on the spring post extension about an inch or two without coming dislodged, if you are running longer-than-needed shocks, but make sure the shocks don’t allow the ACOS to slide off of the spring post.
2D) If using factory ZJ rear coils, you MAY have to open up the “pigtail” on the coil springs slightly, to get them over the threaded section of the ACOS spacer. This is normal for factory ZJ coils, and can easily be remedied with a right angle grinder or hack saw, clearancing only the tip of the coil spring where it contacts the ACOS threaded section and the internal “locating ring” once the spring fully seats.
That’s it. Really simple. Done deal.