| Anti-lock brake system | |
| A device attached to a mechanically driven cooling fan that allows the fan to freewheel when the engine is cold and the vehicle is driven at speed. | |
| A flexible coupling between two shafts that allows each shaft to maintain the same speed regardless of operating angle. | |
| A plug used to fill holes in a block or head left from the casting process. Also called freeze, welsh or expansion plugs. |