Automatic transmissions are actuated via hydraulic pressure, and always have been. Older ones controlled said hydraulic pressure via mechanical and vacuum actuators, newer ones control the hydraulics electrically.
This. I had a Toyota Cressida that broke its timing belt. It simply quit in mid-flight, allowing me to coast to the side of the rural road, with no bangs, screeches or other unusual sounds. The engine turned over fine; in fact it turned over a bit quicker than usual because it wasn’t trying to turn against the compression stroke on any cylinder. On replacing the belt, it ran just fine for another three years.
Now, ask me what ejecting the spark plug on a Honda Civic sounds like.
What does ejecting the spark plug on a Honda Civic sound like?
Well, there I was, pulling up to a red light when there was a loud, tinny bang followed by less tinny metallic thumps each time the cylinder tried to fire. Since the car speed and engine RPMs were both declining at the time, my first thought was that I’d run over something and it was trapped in the wheel well. It kept up after we’d stopped though and I’d no sooner drawn a mental pencil line through that hypothesis when the light changed. I drove through the intersection and pulled into a handy bus pocket that was not being used and shut off the engine.
After opening the hood and a quick examination, everything seemed perfectly okay. The spark plugs are vertical on the engine and down a well so the offending assembly was right where it should have been, plug wire attached to the boot and all. DesertRoomie watched while I started the engine and she immediately cried, “Stop! Stop!” Constrained by the wire, the loose plug was trying to leap out of the well so most of the boot was exposed, then falling back in just in time to be blown out again. Stop engine, close hood, and call AAA. While waiting for the tow I noticed the reverse dimple in the hood.
It was in town so I got towed to my favorite shop. Next day when they could get to it, a Heli-Coil fixed things right up. They said they’d never heard of anything like that happening spontaneously.
Losing a spark plug on most four-cylinders sounds more or less the same - like you’ve lost a cylinder. Listen from about 1:00 here.
ETA: But apparently not on a Civic.
Any chance the threads were stripped when the plugs had been changed at some previous time? Was that an aluminum block?