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This 2002 Honda Accord EX with 138,000 miles,  came in in because the owner was hearing a noise while driving the vehicle. She described it as a rattle or rotational squeaking. While doing a vehicle inspection our tech discovered that her subframe was broken at the right side of the sway bar bushing.

 

A subframe is a structural component of a vehicle, such as an automobile or an aircraft, that uses a discrete, separate structure within a larger body-on-frame or unit body to carry certain components, such as the engine, drivetrain, or suspension . The subframe is bolted and/or welded to the vehicle. When bolted, it is sometimes equipped with rubber bushings or springs to dampen vibration.

The principal purposes of using a subframe are, to spread high chassis loads over a wide area of relatively thin sheet metal of a monocoque body shell, and to isolate vibration and harshness from the rest of the body. For example, in an automobile with its powertrain contained in a subframe, forces generated by the engine and transmission can be damped enough that they will not disturb passengers. As a natural development from a car with a full chassis, separate front and rear subframes are used in modern vehicles to reduce the overall weight and cost. In addition a subframe yields benefits to production in that subassemblies can be made which can be introduced to the main bodyshell when required on an automated line.

There are generally three basic forms of the subframe.

  1. A simple “axle” type which usually carries the lower control arms and steering rack.
  2. A perimeter frame which carries the above components but in addition supports the engine.
  3. A perimeter frame which carries the above components but in addition supports the engine, transmission and possibly full suspension. (As used on front wheel drive cars)

A subframe is usually made of pressed steel panels that are much thicker than bodyshell panels, which are welded or spot welded together. The use of hydroformed  tubes may also be used.