For 1997, Ford redesigned its F-150 SUV variant. To accommodate changing segment demands, the three-door (with lift-off hardtop) Bronco was replaced by the five-door Ford Expedition. While sized between the Chevrolet Tahoe and the Suburban, the Expedition was fitted with three-row seating (offered by the larger Suburban). For 1999, Ford expanded the F-Series model range, with the F-250 and F-350 becoming the Super Duty series. Intended for work usage and towing, Super Duty F-Series trucks received a heavier-duty chassis and suspension along with a distinct body design. To compete against the 2500-series Suburban, Ford began the development of a heavy-duty SUV derived from the -ton F-250/1-ton F-350 Super Duty pickup truck, called the "Excursion". Design overview Chassis The Ford Excursion was produced sharing the platform architecture of the F-250 Super Duty pickup truck. Alongside a shared 137-inch wheelbase (from the Super Cab, short bed), the Excursion shared common body and chassis assemblies with its F-250 counterpart. To allow for a common front and rear track width, the front suspension and most of the rear suspension were common components (the Excursion was fitted with its own leaf springs and front spring hanger bracket). The Excursion was fitted with a distinct frame (differing from the front sway bar mounts rearward), leaving the model taller and wider than its pickup truck counterpart. The rear axle for all Excursions was a Sterling 10.5 axle. The four wheel drive models were equipped with a NV273 transfer case and Dana 50 front axle. Gear ratios of 3:73 and 4:30 were offered. During the development of the chassis, Ford learned that its initial design caused smaller vehicles (such as a Ford Taurus) to become severely overridden in a head-on collision. In the test, the tire of the Excursion drove up to the windshield of the Taurus (reducing the chance of survival for its driver). As a response, Ford modified the chassis to include an under-bumper "blocker beam"; the device was initially tested by the French transportation ministry in 1971. For the rear of the chassis, Ford chose to include a trailer hitch as standard equipment in production to reduce underriding in rear-end collisions by smaller vehicles. Powertrain During its entire production, the Excursion was offered with both gasoline and diesel engines. The standard gasoline engine was a 5.4 L Triton V8; a 6.8 L Triton V10 was offered as an option. At its launch, the optional diesel