"Galloping," or speed related "hopping".

No argument, I have never seen a truck fall off of a dyno, I have seen a truck fall off of jack stands. I am curious why a person with your screen name would think this is " OK " and safe.

 

You've seen a truck "fall" off jack stands? I'm guessing there was jack involved.
You could run a truck against the governor in high gear if supported properly. The only way it would go anywhere is if it had a bad inbalance then it might hop off. It still would not go anywhere if the operator has enough sense to let out of the throttle.
The mass of the truck versus the relatively small kinetic energy of the rotating tires would be a spectacular dissapointment if you were looking for catastrophic disaster.
My advice and the one overlooked so far is clean all the rocks out of the tires.

 

Heck, that's how I polish my rear wheels, just jack her up and let it idle in 4th or so.

Gotta keep your knuckles out of the lugs and valve stem though!