If enabled, gearboxes will deny shifts that might cause damage as well as prevent certain mode changes for a more immersive racing experience. (For example shifting out of M mode is disallowed until you are below a certain speed)
Bring your own vehicle in this never-ending scenario. The question isn't whether your vehicle will be wrecked, but when. How long can you last for? In this scenario you'll have to keep avoiding the never-ending flow of obstacles