It sounds like the axles got swapped from one side to the other, usually the left axle breaks first I have broken two stock 8 3/4 axles with posi, none since I bought Strange race axles. I also switch to 35 splines with the new axles and spools I now run a Dana 60 with the same 35 spline race axles as I started with 6 years ago in the 8 3/4