Without knowing your mechanical experience, forgive me if I assume wrong, but are you installing the U-joints correctly? If you are, a bent drive shaft will cause premature wear and will fail. Also, if any of the balancing weights have broken off the drive-shaft, it will be "Out of balance" and cause a failure too. Additionally, if you do any "Mudding", accumulation of mud or debris that sticks to the shaft can cause an out of balance situation. If you have any type of lift kit on your truck, it can put undue stesses on the U-joint too.
Sunday, October 18th, 2009 AT 8:24 AM