Following similar paths mapped out by the all-new '02 Explorer, the Ford Expedition appears bigger, stronger, faster, and probably safer than the vehicle it replaces. Certainly, the technology is impressive. Engine mods, suspension engineering, body building, frame strengthening, four-wheel-drive upgrades, improved towing capacities, and industry-first interior tricks all add up to one of the most thorough makeovers we've seen to date.
A new hydroformed frame is more than 70 percent stiffer than the previous platform. This bonus allows engineers more precision in tuning the frame for better compatibility with specially designed suspension components, crossmembers, and body mounts. Probably the most unique feature to this Expedition is the use of an independent rear suspension, similar in structure to that on the new Explorer, but with a slight difference. To allow the Expedition more rear-wheel travel during uneven road surfaces (potholes, rocks, etc.), Ford engineers designed an oval portal through the frame, rather than the round hole of the Explorer, to provide for more up and down flexibility. The advantages of IRS include better on-road ride and handling, less weight, and greater center-differential ground clearance, but are sometimes thought to be less durable. Ford seems to have compensated for this by offering the Expedition with two of the largest ring-and-pinion sizes in its class for both engine options (8.8 in. with the 4.6L V-8; 9.8 in. with the 5.4L V-8), and providing for an ultra-stiff, oversize, cast-aluminum rear-differential cover to help fight driveline flex and whine. Standard cast aluminum upper and lower control arms hold the wheels, while a choice of coil-over or airbag-suspension systems damp the jounce. The air-springs option offers an automatic lowering (at highway speeds and in Park) and raising setting (when in 4x4 low range) where appropriate.
Although these two engine sizes were offered with the introduction of the Ford Expedition in '98, both have been refined and improved to limit noise, vibration, and lost horsepower. The 4.6L SOHC V-8 has had the most changes, including an all-new aluminum block, new mounts, extensive use of composites, and a metal-plastic oil pan to further reduce vibration. The 5.4L uses an all-new computer-designed cast-iron block and numerous other upgrades specifically designed to, likewise, limit noise and vibration. Both engines have torque ratings several hundred rpm lower and offer better fuel-economy numbers than the previous V-8s. These powerplants will continue to rely on the 4R70W four-speed automatic transmissions that now benefits from a more powerful computer, able to read and predict work load and compensate where needed.