Body on frame vs. unibody: Pros and cons

Once common throughout the industry on a variety of vehicle types, this method of construction is now largely limited to pickups and SUVs. As the name suggests, these vehicles use two separate components for the vehicle’s frame: a ladder-type frame sits under the body itself.

This ladder frame resists twisting better than a unibody vehicle, so it’s generally preferred for towing or carrying heavy loads and for aggressive off-road driving. It’s also easier to modify these vehicles’ suspensions to make room for additional wheel travel or larger tires and wheels.

This method was also preferred in the earlier days of the automobile because automakers could make annual changes to their vehicles’ body styles while keeping the same frame underneath; they could also use distinct bodies on the same frames.

But as the industry increasingly shifted to the unibody setup, fewer and fewer vehicles stayed with this old-school setup. Aside from today’s SUVs and pickups that continue down the body-on-frame path, some large sedans were the most recent holdouts. Notably, Ford’s Crown Victoria and Lincoln’s Town Car — workhorses of livery services for years — rode on Ford’s Panther rear-wheel-drive, body-on-frame platform until they were discontinued in 2011.

This setup integrates the frame into the body construction so it’s a single piece. Because it doesn’t rely on heavy steel rails like those of a body-on-frame vehicle, unibody construction cuts significant weight out of the vehicle, allowing for better fuel economy. It also offers better handling and ride comfort and is safer, since the entire body can absorb the energy forces in a crash.

This construction method isn’t new; the Ruler Frameless from 1915 is among the earliest examples of automakers looking beyond the traditional body-on-frame setup. Throughout the 1930s and 1940s, the unibody setup began to gain popularity and was common by the 1960s. 

Jeep’s second-generation Cherokee — which debuted in the early days of the SUV craze in the U.S. in 1984 — was actually unibody, making it rare among its truck-based contemporaries. It wasn’t until Toyota’s RAV4 debuted in 1994 that unibody (and car-based) crossovers really took off. 

The merits of unibody even lured in Honda, which has built two generations of its Ridgeline pickup on a unibody platform.