The upper ball joint goes in from the top, and getting it in just plain sucks. The bottom of the mounting flange in the axle is curved and the spacer won’t sit flat against it. After trying several methods, we found that using a couple of shims on the outboard edge of the spacer (shown) allowed us to press the ball joint into place. Make sure the shims don’t block the path of the ball joint. This looks scary and it is, but it was the only way we could get the ball joint pressed all the way in.