I have a 1999 blazer 4.3 vortec,4L60E,4X4,4 Door on the dyno its pumping out 274hp and 336ft ilbs tq with the help of just about every bolt on modification avalible and started having problems with the 7.625 rearend so I rebuilt the complete rearend everything new except the ring and pinion and axles put a new auburn posi unit in at the same time now the posi keeps knocking the axle bearings out. Only used the best parts avalible and everything is setup correct with proper gear oil and additive. Has anybody ever had this problem and if so any solution? The problem is that after a few hundred miles the rotors will start rubbing the caliper brackets put new bearings in nd a few hundred miles later it happens again.

 

Have you replaced the axle shafts themselves?