ZJ coils are longer and stiffer, if you compare I6 wrangler coils to V8 grand cherokee coils, I installed them in my TJ.
XJ coils are the same as TJ coils
Hasn't come off yet...just make sure the mating surfaces are really clean and roughed up. I used a small wire brush on my dremel tool to scuff them up both the axle and the puck....
Besides they'll only get pressed on harder and the axle does not move sideways the track bar prevents that.
I used black RTV to "glue" a hockey puck to each of the spring locators on the both of my axles, if you need more than 3/4 of an inch screw two of them together and then glue them on. I would not use more than two but I have seen a guy that screwed five of them together and just put them in the...