I put down 430RWTQ and they didn't let loose. The splines would hold probably 900+ ft/lbs of loading. The universals/CV's would let loose before that I'm sure, but its the shockloading that breaks things. Dropping the clutch causes the torque delievered to these components to skyrocket, especially in 1st gear. Its that quick spike in torque as the engine's RPM is absorbed that breaks these parts. It would be interesting to see a plot of the torque over distance for a launch. Hmmmmmm.