mechanic58

The u-joints used on the stock shafts are plenty strong - the reason these shafts fail in the middle is a result of the design. Typically the slip joint on a one-piece driveshaft (a driveshaft with no center support bearing) is on one end or the other - not the middle. They are not affected by harmonics nearly as much as a joint in the middle of the shaft would be. On the new Mustang shaft, the joint in the middle gets subjected to severe vibration at high shaft speeds and because of its design it fails. Doesn't have anything to do with the added twist of the supercharger or whatever. It's 100% related to shaft speed and poor design.

This is why the newer GT cars with manual transmission all have a 2-piece shaft design. Those cars typically have lower final drive ratios and higher driveshaft speeds. Same reason why all heavy duty trucks have driveshafts with multiple sections with support bearings - they're geared low and typically have high shaft speeds.

The higher your driveshaft speed, the more critical it's design. Lots of science in driveshaft design.

Nuke

Sorry to hear that. There have been plenty of threads about both the 4.0 and 3.7 stock DS failing at 120+ speeds.