The device used in a vehicle equipped with an automatic transmission. Used to change gears, taking the place of a clutch, in a manual transmission. Has many downfalls, but commonly used in the United States because, sadly, no one can drive stick anymore. For example, the hydraulic fluid can be starved on hills, leading to transmission failure. While pulling large loads, the converter may overheat, which is why it is not used for large trucks. Robs the engine of power, as power is lost in the conversion process. Fuel efficiency is also lost, same reason as above. Excessive repair costs, as the fluid in the converter is required to be replaced every so often.