Six-wheel drive (6WD or 6×6) is an all-wheel drive drivetrain configuration of three axles with at least two wheels on each axle capable of being driven simultaneously by the vehicle's engine. Unlike four-wheel drive drivetrains, the configuration is largely confined to heavy-duty off-road and military vehicles, such as all-terrain vehicles, armored vehicles, and prime movers.
When such a vehicle only has six wheels by definition all are driven. When it has ten – with two pairs of ganged "dual" wheels on each rear axle as on a GMC CCKW – all are also driven but the 6×6 designation remains. For most military applications where traction/mobility are considered more important than payload capability, single wheels on each axle (often referred to as super singles) are the norm.
Heavy hauler and ballast tractor 6×6s have had a long history as prime movers both in the military (as tank transports and artillery tractors), and commercially in logging and heavy equipment hauling both on- and off-road.
Most six-wheel drive vehicles have a forward axle and two at the rear (with only the front pair steering), or three evenly spaced in varying steering configurations. Depending on the vehicle's role, the number of wheels varies between six (in three pairs) and ten (with two in the front and two dual axles with four wheels apiece in the rear). Drive may be limited to the rear two axles for on-road use.
Concept car, testbed, and limited production commercial examples include:
Twin front axle
Twin rear axle
(Twin axle) drive in the rear, and an integrated "roll steer" function built into the suspension design. All 6x6 Australia Pty Ltd vehicles are ADR-compliant with IPA for both "heavy" and "light" vehicles.
A semi-tractor-trailer truck is the combination of a tractor unit and one, or more, semi-trailers to carry freight. A semi-trailer attaches to the tractor with a type of hitch called a fifth-wheel.
The Unimog is a range of multi-purpose all-wheel drive medium trucks produced by Daimler AG and sold under the Mercedes-Benz brand. In the United States and Canada, the Unimog was sold as the Freightliner Unimog.
An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported. In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type axle is referred to as a spindle.
Four-wheel drive, also called 4x4 or 4WD, refers to a two-axled vehicle drivetrain capable of providing torque to all of its wheels simultaneously. It may be full-time or on-demand, and is typically linked via a transfer case providing an additional output drive shaft and, in many instances, additional gear ranges.
A dump truck, known also as a dumper truck or tipper truck, is used for transporting dumps for construction as well as coal. A typical dump truck is equipped with an open-box bed, which is hinged at the rear and equipped with hydraulic rams to lift the front, allowing the material in the bed to be deposited ("dumped") on the ground behind the truck at the site of delivery. In the UK, Australia, South Africa and India the term applies to off-road construction plant only, and the road vehicle is known as a tipper lorry, tip-truck, tip-trailer, tipper truck, or tipper.
Portal axles are an off-road vehicle suspension and drive technology where the axle tube or the half-shaft is off-set from – usually above – the center of the wheel hub and where driving power is transferred to each wheel via a simple gearbox, built onto each hub. This gives two advantages: ground clearance is increased, particularly beneath the low-slung differential housing of the main axles — and secondly, any hub reduction gearing allows the axle halfshafts to drive the same power but at reduced torque. This reduces load on the axle crownwheel and differential.
The Medium Tactical Vehicle Replacement (MTVR) is a series of vehicles, based on a common chassis that vary by payload and mission requirements. The MTVR is a purpose-designed military vehicle, although a small number of vehicles have been sold commercially for specialized operations such as wildfire fighting.
A dolly is an unpowered vehicle designed for connection to a tractor unit, truck or prime mover vehicle with strong traction power.
The Mercedes-Benz Actros is a heavy-duty truck introduced by Mercedes-Benz at the 1996 Commercial Vehicle IAA in Hanover, Germany as the replacement for the SK. It is normally used for long-distance haulage, heavy duty distribution haulage and construction haulage. It is available in weights starting at 18 tonnes and is powered by an inline-6 diesel engine with turbocharger and intercooler. Daimler Trucks/Lorries launched the version II of the Actros in 2002, and the version III in 2007. The fourth generation of the Actros, named officially "the New Actros", launched in July 2011.
A tractor unit is a characteristically heavy-duty towing engine that provides motive power for hauling a towed or trailered-load. These fall into two categories: heavy- and medium-duty military and commercial rear-wheel-drive semi-tractors used for hauling semi-trailers, and very heavy-duty typically off-road-capable, often 6×6, military and commercial tractor units, including ballast tractors.
Eight-wheel drive, often notated as 8WD or 8×8, is a drivetrain configuration that allows all eight wheels of an eight-wheeled vehicle to be drive wheels simultaneously. Unlike four-wheel drive drivetrains, the configuration is largely confined to heavy-duty off-road and military vehicles, such as all-terrain vehicles, armored vehicles, and prime movers. Other types of smaller 8x8 vehicles include such things as the Argocat.
Ten-wheel drive, 10WD or 10×10 is a drivetrain configuration of ten wheels, all of which are driven simultaneously by the engine. Unlike four-wheel drive drivetrains, this configuration is only used in extreme off-road and military uses, in particular heavy duty uses, such a heavy haulage and missile carriers. It is also used in lorries.
Twelve-wheel drive, 12WD or 12x12 is a drivetrain configuration of twelve wheels, all of which are driven simultaneously by the engine.
The "New Generation“ is a series of trucks by Daimler-Benz built from 1973 to 1988. It was then replaced by the Mercedes-Benz SK series. With the "New Generation", Daimler-Benz expanded its market position in the medium and heavy truck segments. Its cab was also used by Mercedes-Benz of North America, who confusingly offered it with inline-six or -five engines as the LP series beginning in 1985.
The Mack M123 (G792) was a 10-ton 6x6 semi-tractor introduced in 1955; the Mack M125 was a heavy cargo truck version of the M123. The M123 was used to tow tank transporter trailers while the M125 towed field artillery pieces.
A 6×4 drivetrain (six-by-four) is a vehicle with a drivetrain of three axles delivering power to two wheel ends on two of them. It is a form of four-wheel drive but not one of all-wheel drive.
The HX family are a range of purpose-designed tactical military trucks manufactured by Rheinmetall MAN Military Vehicles (RMMV). The HX range was disclosed in 2003, and the first order was placed in 2004. The HX range replaced the earlier FX and LX ranges in production. The HX2 range, which currently complements the original HX range, was announced in 2012. The first HX2 range trucks were delivered in April 2016. The HX and HX2 ranges originally complemented the SX range, but as of 2019 they had replaced the SX range as the type was no longer produced.
The 2 1⁄2-ton, 6×6 truck was a standard class of medium duty trucks, designed during the beginning of World War II for the US Armed Forces, in service for over half a century, from 1940 into the 1990s. Also frequently known as the deuce and a half, or just deuce, this nickname was popularized post WW II, likely in the Vietnam war era. The basic cargo versions were designed to transport a cargo load of nominally 2 1⁄2 short tons over all terrain, in all weather. The 2 1⁄2-ton trucks were used ubiquitously in World War II, and continued to be the U.S. standard medium duty truck class after the war, including wide usage in the Korean and Vietnam Wars, as well as the first Gulf War.
Rheinmetall MAN Military Vehicles (RMMV) TG MIL range of trucks is based on MAN TG range commercial chassis that are militarised to suit individual customer requirements. The TG MIL was introduced from 2010 when RMMV was established in January of that year. RMMV was initially the merger of Rheinmetall's wheeled military vehicle activities with those of the military truck activities of the now MAN Truck & Bus AG, but from 2019 the joint venture focuses only on logistic vehicles. Prior to 2010 militarised TGM and TGA range trucks were products of the now MAN Truck & Bus AG.
The Mercedes-Benz L 4500 is a heavy duty truck by Mercedes-Benz. It was built by Daimler-Benz from 1939 – 1944 in the Mercedes-Benz plant Gaggenau, and from 1944 – 1945 by Saurer. The vehicle is a long-bonnet truck and was offered as a rear-wheel-drive truck and as an all-wheel-drive truck. The German Wehrmacht used the L 4500 with armoured cabins as Flaks during World War II. Due to the lack of production material, the cabin was replaced with the simplified standardised Wehrmacht cabin and the mudwings with simplified wings in 1943. Also, the L 4500 chassis was used for the Sonderkraftfahrzeug 4.