The frame of a vehicle is what the body and powertrain parts are mounted to. It is literally the backbone of the vehicle.
Types of Frames
There is only a handful of frames that are used on vehicles. These are the most popular.
- C shape
- Box
- Subframe
- Unibody
C Shape [
The c shape frame was the most common frame used on pickup trucks. It has been replaced by the box frame.
Box []
A box frame is one piece of metal folded into a box of four sides. It is welded on the seam where the piece of metal comes together after it has been folded and is stronger than a c shape frame. These frames can be found on trucks and full size vehicles.
Subframe
A subframe is a small section of a frame that is typically used to support the engine and/or transmission in the front of a vehicle. It may be used under the rear of a vehicle and provide the mounting surface for the suspension and driveline components. Subframes can be made of steel or aluminum. They are typically used on vehicles that do not have full frames.
Unibody
A unibody is a frame that is integrated into the actual body of a vehicle. It is not a separate piece. The construction of the body is engineered in a way that the body can carry the load of the vehicle. Subfames are used with this type of frame to carry the powertrain components.
Parts of a Frame
There is only two parts of a frame really worth mentioning for our purpose. They are typically only found on the c shape and box frames.
Side Rail
The side rails are the parts of a frame that run front to back on the left and right side of the vehicle.
Crossmember
Crossmembers run perpendicular to the frame side rails. They are generally welded in place and stabilize the whole frame.