cracked a ring gear bolt

just being curious. Is that happened to someone else? I was torquing them not even close to specs (55 lb ft ). Guess i had 40 lb ft at that Point around and the bolts felt kinda soft and one cracked.
Not sure but i got my bolts from drDiff. Can it be they were grade 5 instead of grade 8? I mean I have no clue wherelse the the error could be. All is brand new. Ring&pinion, bolts, eaton truetrac.........