i ment the third houseing.. should have been easy to pick up since i mentioned the ribs.. but anyway. the ring gear deflects because the pinion is trying to walk on it  and pushes the ring gear away which =  boom

on the housing.. go look at one and just look at the weld that holds the 2 halfs together . thats where they start to peel and crack and then it travels up around the spring perch weld.. its not a good design.. and on the later model housings they smash around the perches.  this is extremely normal.. if you go look in lilbuddy's thread you will notice his  axle housing did the same thing  and i know he isnt as hard on his rig as i am on mine.