I'm guessing about 550 hp on a 4.30 sure grip rear end with M/T cheeter slicksHow much power are you running? Stock axles vary but if you are running a spool, then the pucker factor goes up and you need to watch them closer. Doesn't make a bunch of sense but a locked up rear end places a good deal of stress on them. Why not contact Dr. Diff and see what he has. I know he has a higher strength ones available.....