The crush/solid sleeve provides the preload on the bearing. If you torque the crush sleeve to much you completely destroy it and have to replace/start all over. The solid doesn't do this and once you have the correct spacing/preload you can change a pinion seal and retorque with no problem, not with the crush. This crush sleeve is the weakest part in the 489 once changed it becomes a moot point. ALL of my 489 have a solid sleeve in them.