6×4

Typical American 6×4 tractor unit

A 6×4 or six-by-four is a vehicle with three axles, with a drivetrain delivering power to two wheel ends on two of them.[1] It is a form of four-wheel drive[2] but not one of all-wheel drive.

It is the most common form of drivetrain of semi-tractors[2] and heavy haul fixed-chassis cargo trucks in larger countries such as the United States and Australia; in Europe, 4×2 and 6×2 variants are more commonplace.

Supplementary axles

TACR2 airfield fire engine

Nearly all 6×4 have an unpowered leading steering axle, with two driven rear axles. However some mass-produced 4×4[i] vehicles have had their load-carrying capability increased by adding an additional, unpowered, rear axle.

The Carmichael Commando chassis, a stretched version of the Range Rover, was used for such extended 6×4 conversions in the 1970s and '80s. Some German conversions provided full 6×6 performance, but most were like the TACR2 and just 6×4. This gave a vehicle suitable for airfield emergency services; with fast performance on tarmac, useful off-road performance for crossing obstacles, increased load capacity and a much cheaper price than dedicated 6×6 vehicles.

See also

References

  1. ^ These have been mostly AWD vehicles with permanent 4WD and good road performance rather than the selectable 4WD used more widely for earlier off-road vehicles.
  1. ^ International ProStar ES Class 8 truck: Axle configurations
  2. ^ a b NACFE (North American Council for Freight Efficiency) Executive Report – 6x2 (Dead Axle) Tractors [1] Archived 2015-07-07 at the Wayback Machine "A typical three axle Class 8 tractor today is equipped with two rear drive axles (“live” tandem) and is commonly referred to as a 6 X 4 configuration meaning that it has four-wheel drive capability."