ORIGINAL: mecky33
The diff cups break on the rear diff because the of the dog bones. If you upgrade to CVD's it lowers the risk of breaking diff cups. You can also build sleeves that slide over the diff cup to keep it from spreading, there are a few people on here that have done that.
i made the sleeve by using some 7/16 brass tubing with some aluminum foil underneat to take up the little bit of extra space.