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Frame vs. Unibody Vehicles

A frame or unibody provides a vehicle with structural strength. It is also used for mounting all the other systems that comprise the total car chassis.

Car frame construction was used in early automobiles and is used in some types of vehicles today. In a car frames construction, the frame is made of steel and designed so that the body of the vehicle is mounted on top of it. The unibody is actually stamped out as part of the vehicle's structure. Today's passenger vehicles most commonly use unibody construction because of its ability to absorb energy during a collision.

The National Auto Auction Association (NAAA) uses the following diagrams and descriptions for frame identification in its Structural Damage Policy.

Unibody Construction

Unibody car frame construction
Image: NAAA

Frame Construction: Ladder and Perimeter Frame

Car frames: Ladder and perimeter body-on-frame construction
Image: NAAA