that is certainly a reason they break but it also has to do with the width of the ring gear, being as it is smaller to accomadate the extra teeth and the pinion is also, correct? That is what i hear and i have seen them break. I daily drove my truck with 36's and 4.10 gears for quite some time and at times it sucked but i dealt with it. Put your money in the T-cases thats what i say!