There's no harm done. I always test the transmission that way, the rear end for stress factors.
6 seconds sound clip from the Fear and Loathing in Las Vegas movie soundboard.
You can hear this line at 00:09:59 in the Blu-ray version of the movie.
Quote context
[...]
- Listen, you're gonna be real careful with this car, right?
- Holy smokes! You just backed over a two-foot concrete abutment, and you didn't even slow down.
- What were you going, about, uh, oh, I don't know, 45 miles an hour backwards?
- There's no harm done. I always test the transmission that way, the rear end for stress factors.
- Boy, this is really a nice pen, man.
- Hey, uh, listen, you... You fellas haven't been, uh, drinking, have you?
- No. Not me. We're responsible people.
- Goddamn it, you've got my pen!
[...]