If your leaking gearoil out the pinion it will not be the crush sleeve causing the problem. more than likely you have some wear on the bearing or the race. The crush sleeve is for helping with the pinion depth. If the seal is leaking it will more than likely be caused from the same problem. Seals go out from old age (drying out) tear, or the bearing having to much play. Like mentioned above check the vent to make sure that it is not plugged. Is it possible that it got over filled?