Exhaust brakes and the magic behind the infamous noise.
Everyone has heard it: a long-nose Pete going downhill on the highway, giving off a loud “duh-duh-duh-duh-duh” slowing gradually as the truck loses speed. That would be the ever well-known engine brake. (a.k.a. Jake Brake) A diesel exhaust brake, commonly used in medium duty diesel pickups is a not too distant cousin.