You don't HAVE to take it apart! Get a friend and two axles. Lay the unit on the floor and insert both axles. Have your friend hold one axle and you grip the other. Then turn the axles against each other. Your buddy turns one way and you the other. The unit should not slip or even "click". Whichever of you is stronger should be able to turn the other over without the unit ever having any "give"
I've seen blown units that would freely turn like an open rear (obviously blown) and some that would slip a little when the pressure was put on it (starting to go).
