Back to GuidesA body-on-frame vehicle has a chassis that is separate and then attached to a vehicle’s body whereas, in a unibody design, the vehicle frame and chassis are made as one single unit. Most trucks and a handful of SUVs are made using a body-on-frame construction. Cars, minivans, and most SUVs, called crossover SUVs, feature a unibody construction.
Body-on-frame construction and unibody construction are the two most common ways to build a car, and both methods offer advantages to buyers.
To understand why the battle of unibody vs. body-on-frame is so important, we have to dive deeper into what each construction method has to offer you as a buyer.
Body-on-Frame: What are the Pros?
Even though body-on-frame vehicles are seen by some as “old school,” there are several advantages they offer over unibody vehicles.
Off-Road Capability:
One of the primary reasons that many pickup trucks and some SUVs like the Jeep Wrangler are so good offroad is because they utilize a body-on-frame design. Unlike the unibody design, body-on-frame construction allows a certain level of body flexing. The chassis underneath the body allows the twisting forces produced by going over uneven terrain to flex the vehicle’s body without hurting it.
This does not mean that unibody vehicles cannot go off-roading, but it does mean that the same twisting forces are transmitted through the entirety of the vehicle itself. The potential for vehicle frame warping is, thus, much higher.
Towing Capacity and Payload:
Another reason that pickup trucks are often manufactured using body-on-frame construction is that they can generally haul and tow more than unibody vehicles. The same flexibility and strength that allows them to traverse rough terrain more easily also allow them to tow more.
Less Expensive Manufacturing Process:
Body-on-frame vehicles are usually less expensive to manufacture because of their two-piece design. A single chassis and powertrain can be used across several different bodies to create several different vehicles. In a unibody design, the entire unit has to be manufactured differently to produce different vehicles or even the same vehicle model in different sizes.
Overall Ruggedness:
Beyond hauling, towing, and off-roading, body-on-frame vehicles tend to be tougher than unibody vehicles. This is one reason Ford Crown Victoria Police Interceptors were so loved by law enforcement, despite being so slow. They held up to enormous torture, and the many that are still on the road serve as a testament to their overall strength.
Additionally, if one piece of the vehicle is damaged, it can be more easily replaced. A notable example of this is the rust issues experienced by Toyota Tacoma owners several years ago. Toyota was simply able to replace the frame of the truck instead of the entire truck itself to rectify the issue.
Body-on-Frame: What are the Cons?
There are several drawbacks to body-on-frame construction, many of which contribute to the fact that unibody vehicles are much more prevalent in the current automotive market.
Weight:
Usually, when you have more of something as opposed to less of the same thing, the thing with the larger amount is also going to be heavier. This is the case with body-on-frame vehicles. Since two pieces are utilized to construct the vehicle, they are heavier than the single unit that makes up most unibody vehicles.
Less Refined Driving Dynamics:
Strength and ruggedness come at a cost. If you have heard the phrase, “it rides like a truck,” this is because trucks and body-on-frame SUVs tend to be less comfortable on the road. They also do not handle as well and have a higher tendency for rollovers due to their increased ground clearance and higher center of gravity.
Harder to Make Safe:
Body-on-frame vehicles tend to be less safe than unibody vehicles overall. It is more difficult to integrate advanced safety systems into their design, including crumple zones. This does not mean that they are not safe as modern technology has made vehicles much safer than they used to be. It just means that they are usually not as safe as their unibody counterparts.
More About Body-on-Frame Construction:
There are several different types of body-on-frame construction that exist. Ladder frame, space frame, and perimeter frame have been among the most popular types of body-on-frame constructions, but other designs like the X-frame and backbone chassis have been used with lesser success.
Because of their limitations, body-on-frame vehicles, especially SUVs, have decreased in popularity in recent years. There are still several models that use this construction, though.
The Jeep Wrangler, Toyota 4Runner, Toyota Sequoia, Ford Expedition, Chevrolet Suburban, Chevrolet Tahoe, Cadillac Escalade, GMC Yukon, Lincoln Navigator, Nissan Armada, and Lexus LX600 are some of the truck-based SUVs still available on the market.
Pickup trucks like the Ford F-150, Chevy Silverado, RAM 1500, Toyota Tundra, Nissan Titan, Jeep Gladiator, Toyota Tacoma, Nissan Frontier, Ford Ranger, GMC Canyon, and Chevy Colorado are also built using body-on-frame construction.
Unibody: What are the Pros?
The vehicle frame debate is subjective based on your wants and needs, but the advantages of unibody design are important in the current automotive market.
Fuel Efficiency:
Because they tend to be lighter than body-on-frame vehicles, unibody vehicles also tend to get better fuel economy as a direct result. This is one of the biggest reasons that crossover SUVs have become so popular with manufacturers and buyers.
Safety:
Another huge reason most passenger vehicles have migrated to primarily unibody designs is for the safety advantages they bring. Integrating crumple zones and safety features into a unibody vehicle is much easier than doing so on a body-on-frame vehicle.
Driving Dynamics:
Unlike more serious off-roaders like the Jeep Wrangler, Toyota 4Runner, and some pickup trucks, even non-performance passenger cars, and SUVs with a unibody design have better cornering ability than their truck-based counterparts. Most also offer a more comfortable ride, even if they are large crossover SUVs.
Crossover SUVs are popular because of this fact. You can have a vehicle closer to the size of a pickup truck with some of the comforts that a passenger car has because of how it is built.
Unibody: What are the Cons?
Despite the unibody’s drawbacks, many of these are seen as disadvantages that can be easily overcome by the many advantages that come with this type of vehicle frame.
Less Rugged:
Most people will never take their vehicle over anything more than a rough dirt driveway. Many crossover SUVs and even cars and minivans also offer an all-wheel-drive powertrain option in case of messy weather. Since most road vehicles are just that, this disadvantage is less of an issue than something like driving dynamic drawbacks are for body-on-frame vehicles.
Repair and Manufacturing Costs:
Repair costs are a much larger issue for unibody vehicles. When damage occurs, it has the potential to affect a large portion of the vehicle, since any damage also affects the entire body. Several parts of the body may have to be completely reconstructed in case of severe damage to return the car to its normal operating and visual states.
Even though they are easier to design, they are also more expensive to manufacture. This is because alterations need to be made for each new car model. Even two of the same vehicles may need to be manufactured differently as the frame makes up the entire body.
More About Unibody Construction:
Most vehicles today use unibody construction, but some vehicles, especially high-performance supercars, use what is called a monocoque. Unlike in a typical unibody construction, in vehicles with a monocoque, or “single shell” construction, the vehicle’s body panels are weight-bearing, structurally integral components.
Typical examples of unibody cars include the Toyota Camry, Honda Civic, and Ford Taurus. Unibody SUVs, called crossover SUVs, include the Toyota Rav4, Hyundai Palisade, Kia Sportage, Nissan Murano, Chevrolet Traverse, Honda Pilot, and Ford Escape.
Notable pickup trucks with a unibody frame include the Ford Maverick, Hyundai Santa Cruz, and Honda Ridgeline. Though these trucks are heavily scrutinized by truck purists and enthusiasts for their comparatively low towing and payload capacities, they are still quite capable for their size and are more comfortable than their body-on-frame siblings.
A Brief Frame Design History Lesson:
Body-on-frame design outdates unibody design. All cars before the 1930s were designed with body-on-frame construction. European automakers Opel and Citroen were among the first to experiment with true unibody frames, though Chrysler also attempted a variation of a unibody design in 1934 that did not work well.
Several vehicles in the years to come would start using unibody construction, but it did not truly become popular until the fuel crisis of the 1970s. Today, most new cars utilize a unibody construction.
Notable vehicles that utilize a unibody construction include the Lincoln-Zephyr, Nash 600, Chevrolet Corvair, AMC Eagle, and XJ Jeep Cherokee, one of the first SUVs to utilize this build method. The Ford Crown Victoria and Mercury Grand Marquis are notable for being the last four-door sedans to be made using body-on-frame construction. They remained in production until 2011.
