If you lift from the differential, the axle moves up when you jack, which compresses the springs which you are trying to take out. You pretty much have to use the gas tank method to do this, and I had to remove the rear shocks when I did mine so the springs and springjacks would fit in there. You may have to have someone push up on the opposite side of the axle that you are installing the spring on so that the axle pivots and lets you get the spring in. Don't forget that the bottom of the spring lines up against the metal nub on the axle.