chassis ready for its body The
Ford Model T carried the tradition of body-on-frame over from horse-drawn buggies, helping to facilitate high volume manufacturing on a moving assembly line. The use of steel ladder and X frame
chassis allowed numerous vehicles to share a chassis and drivetrain while making changes to bodywork and interiors relatively easy, thus keeping costs down and minimizing design time. Over time the technology for unibody construction became economically feasible, assisted in recent decades by
computer-aided design. in addition, modern creature comforts, luxury and power-assisted features, and extensive safety reinforcement of vehicles have all added substantial weight; the ability to offset this with unibody construction has proven advantageous. A handful of small passenger vehicles switched to
unibody construction by the end of the 1930s. The trend had started with cars like the
Citroën Traction Avant (1934) and
Opel Olympia (a
General Motors design) introduced in 1935, and the short-lived, aborted
Chrysler Airflow.
Trucks,
bus manufacturers, and large low-volume cars or those made in the United States continued to use separate bodies on "conventional" frames. Body-on-frame remains the preferred construction method for heavy-duty commercial vehicles (especially those intended to carry or pull heavy loads, such as trucks and some
sport utility vehicles (SUVs)) but as production volumes rise, increasing numbers of SUVs and
crossover SUVs are switching to
unibody frames. Mass-market manufacturers
Ford,
General Motors, and
Chrysler are abandoning true body-on-frame SUVs, opting, when sales volume permits, for more efficient unibody construction.
Toyota currently manufactures the most body-on-frame SUVs with the
4Runner,
Sequoia,
Land Cruiser,
Land Cruiser Prado,
Lexus GX, and
Lexus LX, followed by
Nissan with the
Patrol,
Armada, and
Infiniti QX56/80. , ca 1951.
Jensen Motors (of
West Bromwich) built the aluminium-on-ash bodies under contract and transported them to Austin's
Longbridge plant for final assembly. ==Examples==