These work in addition to coils to prevent rear end sag and help carry heavier loads better...not for lifting the vehicle at all...
You need to set the bumpstops for the lift height. so pull the springs & jounce bumper, fully compress the axle on both sides, make sure the shocks aren't bottoming out, check gas tank vs diff cover clearance, check bump alignment, etc.
follow this thread: http://www.wranglerforum.com/f5/corr...gth-70047.html
then once you know what bumpstop extension you need, and get it installed, reinstall the springs and shocks and set the Jeep at ride height.
measure inside diameter of the coils, and the bump height to the bumpstop cup. call up AirLift and tell them those dimensions, and they'll give you a part number to make it all fit.
Parts should be about ~$100, for a shrader valve that can be filled by an external compressor. or you can spend more money for fancy on board compressers and such. max psi is about 35psi for AirLift 1000, so no sense in using a York or something...the AirLift compressor, or a Rancho 9000 shock compressor will work fine and avoid the mess of trying to get a heavy duty onboard with regulator working for this application.
Here's my Airlift bags in the rear:
brass T from hardware store, and black polyethylene tubing (outdoor irrigation tubing)
^i tried the clear PE tubing...don't use it, more brittle in cold and cracks.
I ended up needing to modify the jounce bumpers.
So how do they work?
Normal ride height:
Sagged 3" with ~600+lbs of cargo:
Got an inch back with 20psi:
It drove far more stable and didn't bottom out at all with the Airbags pumped up. No more wishy washy rear when loaded, and no more bottoming out
Here's another write up on AirLift bags:
Jeep TJ Air Lift Suspension Installation Write-Up