Originally Posted by Frank TJ
I was wondering this myself. What I have come up with is this. The owners manual states to disable the QL when changing tires, etc. It also gives specific jacking points that are on the unibody, not any part of the axle/suspension.
What I see is that if you start jacking one corner up without disabling QL it will try to level the Jeep. I can't see how this in itself could cause the Jeep to fall off a jack because the jack is now acting like the missing tire. I personally think it has more to do with the QL getting out of whack and possibly one corner extending to ORII and the rest at normal???
I recently had the tires rotated at the local discount tire. The whole jeep was lifted and all 4 tires were off the ground. We disabled QL and I watched has the Jeep was lifted. The suspension extended to full extension just like any other conventional suspension. If we had not disabled the QL I'm thinking the airbags would continually be pressurized as the jeep was being lifted. This would result in the airbags being at a different setting than the computer thinks they are. Possibly over extension???
Not really sure on this topic. More research needed.
It's not nearly as complicated as you propose. The system will actually try to bleed air from the bladders as the vehicle goes up and since the sensors will not detect a drop in the vehicle the compressor will continue to run until it overheats. This assumes it tries to level, which it shouldn't if the ignition is off and/or a door is open. Locking the system just makes sure it doesn't try.
On thing I've noticed is that when the truck is lifted nitrogen seems to get pulled back into the bladders so when you set it back down it's at roughly ORII height. It does the same whether it's locked or unlocked so obviously there's something going on that's not intuitive. Regardless, it levels out just fine once you unlock it.
As for falling off the jack, it's exactly as you describe, as the system tries to level and it can't lower the side with the jack it will raise the others. Falling off the jack is a worst case event but if you've ever tried to set a car on 4 jack stands one corner at a time you will understand how raising one end can push another end in directions you don't want it to go.