I've broken a few half shafts. I've heard somewhere that due to lube dispersement underway portions of the halfshaft can heat making a weak spot and they'll snap. mine all broke right at the entry to the differential. this always happened when driving for long periods on the highway where vehicle doesn't lean around moving the lube oil. I haven't had a broken axle for over 25 years which i attribute to driving here in the mountains, seldom long on flat and level?