Whats the centering ball bs?
The front propshaft has a double cardon joint, that means 2 u-joints in one unit, they have a centering ball between them, this keeps them aligned and working in harmony.
This ball goes bad, the 2 u-joints then fly apart taking out the whole double cardon joint.
Then the propshaft becomes detached from the transfer case and flops around and puts a nice fist sized hole in the side of your transmission.
You then need to buy a new transmission.

 

Oh I thought it w the u joints that failed... So it's the centering ball..