Carrier bearing trouble???

[feller]

While driving today my 2 piece drive shaft decided to come apart?? Luckily the truck seems to be fine otherwise, and more importantly my dog and I were physically uninjured. My question is, why? The PO told me that the truck had all bearings replaced on drive shaft, so all u-joints and carrier, and thy all look newer than the truck. I had been getting a strange noise/ vibration when cruising at highway speed, but it only seemed to be while in third gear. Originally truck was a 6 with 3 on tree, but was converted to 350/350, if that makes a difference, oh and it was the back half of drive shaft, I don't know if I should trust putting it back together or find a 1 piece. HELP!!!! Lol