I noticed a little trick with these joints when I changed a rack over the summer. The joints and coupler tend to behave like a rigid column when in compression. This "column" needs to "buckle," or fold ion upon itself to allow the u-joint to slide off the splines. If you have the steering wheel oriented in some positions, the lower joint won't, making it impossible for it to slide up and off the splines.

If you have the u-joint bolt all the way out out (the bolt shoulder passes through a groove in the splines to hold the joint to the rack), the slot spread with a hammer, and the thing still doesn't seem to move when you tap it, rotate the steering wheel 1/8 turn or so. Alternatively, loosening the rack will gice you all the slack you need.

Good luck.