I believe the clicking is simply the release of each ball as the joint rotates them out of the position where they're receiving/transmitting torque. Wear causes a little more room for them to move as a small groove is worn into the inner bell and the outer cage - the contact points. As this happens, the ball finishes it's cycle by being popped just like squirting a water melon seed from between squeezed fingers and hits the end of it's travel in the wear groove to make that popping sound. Like a hammer, it will eventually wear that more due to pounding. Fresh moly grease won't change the sound much, but will reduce the ability of the ball to wear the surface somewhat. If someone found birf balls that were a few thousandths oversize, I'd think the popping would be reduced but I think people who've looked have struck out. I don't think the balls sustain any wear - it's the bell and cage they contact.
At 100k, my birfs had both rotational play, and end play. They popped on sharp turns with hard acceleration only and this did not change after I repacked them. On the next repack, I plan to put a new clip in them to reduce the end play, and flip them from R to L and vice versa to start wear in the other direction.
I wouldn't buy new birfs unless you're wheeling hard and have large tires.
DougM
At 100k, my birfs had both rotational play, and end play. They popped on sharp turns with hard acceleration only and this did not change after I repacked them. On the next repack, I plan to put a new clip in them to reduce the end play, and flip them from R to L and vice versa to start wear in the other direction.
I wouldn't buy new birfs unless you're wheeling hard and have large tires.
DougM