Originally Posted by
WindDrake
+1 on that. The plastic shafts flex, so if you're still running into issues after replacing the diff cases and cups, this is something to look into once you're at that point. Shock loads are bad for anything in the driveline.
IMO I don't think they really flex that much, maybe a little at the ends but the splines keep them from twisting much in the middle. Either way I feel the bigger problem is the holes for the universals go from circles to ovals as you use the vehicle. This creates play, backlash and shock loads in the drivetrain.