A 4x4 wrecker is a type of truck used to haul disabled vehicles or otherwise transport heavy vehicles that cannot operate on their own. The function and design of the 4x4 wrecker can vary, though all will have four-wheel drive capabilities that allow it to operate on treacherous terrain or in adverse conditions. Some wreckers will feature a long boom arm that operates in conjunction with a winch system to lift vehicles, while other wreckers may feature a flat bed that can tilt downward toward the ground so a vehicle can be hauled onto it. This system also uses a winch to haul vehicles.
Larger vehicles, such as full-size pickup trucks, tractor trailers, some RV campers, and buses usually cannot be towed with smaller tow trucks. A 4x4 wrecker is usually required to move such vehicles when they become disabled, though the largest wreckers may not be four-wheel drive at all. The largest wreckers can feature three axles with up to ten wheels for added stability and torque. A 4x4 wrecker will generally have two axles, through three-axle trucks with only two drive axles are possible.
If the 4x4 wrecker features a boom arm, that boom may be able to rotate so disabled vehicles off the side of the road can be righted or otherwise hauled back onto the road. While not generally common on these machines, outriggers may be present on the sides of the wrecker to promote additional lateral stability if the vehicle to be towed cannot be positioned directly behind the wrecker. These arms will be controlled by hydraulic cylinders that will extend the arms downward until they rest on the ground. A winch system will be mounted near the cab of the wrecker, and the cable from this winch will run up and over the boom arm so it can be connected to the disabled vehicle.
A flat bed 4x4 wrecker will not feature a boom arm, but instead a flat bed that can be moved in such a way that the back end of the bed tilts down toward the ground. The vehicle to be hauled can be positioned behind the bed, and a winch cable can be secured to the vehicle's undercarriage. As the cable pulls on the vehicle, it will move forward onto the bed, which can be righted slowly into the horizontal position. The disabled vehicle will then essentially ride piggyback on the wrecker.