Whether you have to jack the truck up depends on how many wedges you fit between the springs. I used all three on the front and back of my overload springs which made it pretty tight even when unloaded. If I aired my bags up to 100 psi, I could swing them out and then drop pressure again to 5 psi. If you don't have bags, you can put your jack under your receiver and lift the truck up slightly to swing out the wedges. If you have a trailer attached, cranking up the tongue jack will also relieve pressure (similar to what people do when installing or removing WDH spring bars on their trailer). If you use less wedges, the above extra steps are not needed.