The age is about the norm for shearing bolts. First thing you do is make sure the to redrill the drive shaft tube. I KNOW you stated it is round, but after 6 years, it HAS to have enlarged some. You need to make sure any hardened bolt, that NO threads are in any part of the torque area. The smooth shaft needs to be all the way thru and slightly extend past the exit square shaft tube. The weakest point is if any threads are still contacting the drilled holes in the driveshaft tube. ANY slop in the drift shaft holes will hasten shearing. That is why I advise to cut off the existing tube end and drill a slightly smaller hole and slowly ream the hole out to get a very tight fit when the bolt goes thru. Doug
