I had a friend in college than had a 1950 Ford Truck with a fully built 327 375hp. The hump over the transmission could be removed. He had the hump out and he was giving it some test 1/4 drag runs. Anyway his engine rotated some and broke the four speed transmission case. Parts and oil started to fly around in the cab of the truck.
The driver ended up jumping out at about 30mph. The passenger, his college roommate, was hugging the passenger door when through the mirror he sees the driver sitting on his butt along the road side.
The truck ended up in a gentle roadside ditch unharmed except there was no usable parts , transmission, driveshaft or deferential end
He later got the truck finished and it was a beast.