Chevy Truck 4x4

Four-wheel drive, 4WD, or 4x4 ("four by four") is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously. In the United States, these cars are often, but not always, included in the broader sport utility vehicle category. While many people associate the term with off-road vehicles, powering all four wheels provides better control in normal road cars on many surfaces

In abbreviations such as 4x4, the first figure is the number of wheels; the second is the number of powered wheels. 4x2 means a four-wheel vehicle in which engine power is transmitted to only two wheels: the front two in front-wheel drive or the rear two in rear-wheel drive.

The term four-wheel drive describes truck-like vehicles that require the driver to manually switch between two-wheel drive mode for streets and four-wheel drive mode for low traction conditions such as ice, mud, snow, slippery surfaces, or loose gravel.

The true inventor of four-wheel drive is not really known; the history of such was not well recorded. In 1893, before the establishment of a modern automotive industry in Britain, English engineer Joeseph Bramah Diplock patented a four wheel drive system for a traction engine, including four-wheel steering and three differentials, which was subsequently built. The development also incorporated Bramagh's Pedrail wheel system in what was one of the first four-wheel drive automobiles to display an intentional ability to travel on challenging road surfaces. It stemmed from Bramagh's previous idea of developing an engine that would reduce the amount of damage to public roads.

Designs for four-wheel drive in the U.S., came from the Twyford Company of Brookville, Pennsylvania in 1905, six were made there around 1906; one still exists and is displayed annually. The second U.S. four-wheel drive vehicle was built in 1908 by (what became) the Four Wheel Drive Auto Company (FWD) of Wisconsin (not to be confused with the term "FWD" as an acronym for front-wheel drive. FWD would later produce over 20,000 of its four-wheel drive Model B trucks for the British and American armies during World War I. Thousands of the Jeffery Quad (1913-1919) were similarly used. The Reynolds-Alberta Museum has a four-wheel drive "Michigan" car from about 1905 in unrestored storage.