Shoved it together at the time, and ordered new wheel and axel. When they showed up, pulled the upper rack off of it's tracks, removed old axel. Installing the new axel + wheel was a bit tricky. There isn't anything to hold onto with the wheel in place. Figured the self tapping screw would need the most torque the first time. I went ahead and screwed the screw in the axel alone, to cut threads, took it apart, and then installed it on the upper rack bracket with the wheel. I pressed the axel into its nesting slot to keep it from spinning while installing and tightening the screw. It might have been possible to hold the axel with needle nose pliers, but not how I did it.