A power takeoff (PTO) winch is a hauling device that is operated by the drive train of a vehicle. Splined driveshafts and other coupling methods can be used to connect the transfer case of a vehicle to one of these devices so that the same power that would normally turn the wheels can instead be used to wind or unwind the winch. This can provide a great deal of torque and speed control, though a PTO winch may only be installed on a vehicle that either has a PTO or is designed so that once can be installed. Tractors and four-wheel drive military, utility, and passenger vehicles are all commonly associated with power takeoffs, though the PTO winch has become less common in modern trucks and sports utility vehicles (SUVs) than it once was.
Winches are devices that contain a spooled length of cable or rope which can be unwound and then wound back up. They are typically capable of maintaining tension on the cable during operation, and some can haul very heavy loads. Some winches are operated by hand cranks, though most vehicle winches have some other power method. Electronic winches use electric motors, solenoids, and other components to wind and unwind, while hydraulic winches employ fluid pressure in a manner somewhat similar to power steering systems. A PTO winch is a different variety that actually uses the mechanical power of a drive train.
"Power takeoff" refers to a class of devices that can be operated by the drive train of a vehicle in the same way that the wheels are. In four-wheel drive vehicles, transfer cases are typically used to supply power to the differentials, which then turn the axles that the drive wheels are connected to. If a power takeoff is present in one of these systems, it will usually be part of, or connected to, the differential. The same rotary motion that would normally be transferred to the wheels can then be used to turn a winch or another device.
In tractors, a power takeoff often consists of a splined driveshaft that can be connected to a variety of different devices, such as a PTO winch, generator, or mowing implement, as the need arises. Four-wheel drive vehicles typically use a less modular coupling system, where a PTO winch is connected to the differential by a power takeoff unit. Since modern four-wheel drive vehicles are less likely to be equipped with a power takeoff unit, they typically use electric or hydraulic winches instead.