FWIW here is what critical driveshaft speed looks like. This is with a 4" aluminum shaft, not the vibration in the car down track. The aluminum shaft was fine with a 1050 hp motor due to downtrack driveshaft RPM. But with the 99 Hemi it was not so happy. https://www.youtube.com/watch?v=OBUuEGlJ5ww
