Will IRS Prove To Be One Refinement Too Many?
After providing the popular Explorer with a complete redesign for 2002, Ford has turned its attention toward the Explorer's fullsize brother, the Expedition, which has been significantly reskinned, upgraded, and refined for the '03 model year.
Probably one of the most controversial of those changes is the advent of an independent rear suspension (IRS), making it the only fullsize SUV to possess this feature. The new setup is similar in design to that of the Explorer but uses stronger components. A 9.75-inch differential centersection is used and its halfshafts are stouter than those used on the Explorer to take on the extra weight of the Expedition. Ford claims a total of 9 inches of rear-wheel travel with this new system. So will the new IRS destroy the Expedition's off-highway ability, as it did that of the Explorer? That report will have to wait until we actually get to drive the new Expedition. And how will the IRS hold up to the rigors of towing? Only time will tell us that.
Ford claims that the use of independent suspension at every corner allowed the company's engineers to dramatically improve the ride and handling of the '03 Expedition when compared to the previous generation. Other factors that help improve the ride and handling of the Expedition are its all-new hydroformed frame that is said to be 70 percent stiffer than that of its predecessor. An all-new variable-assist rack-and-pinion steering system also helps to provide better road feel and control when compared to the previous recirculating-ball system.
The Expedition's brakes also were significantly upgraded. Twin-piston calipers squeeze 13-inch rotors in the front, while the rear features single-piston calipers and 13.5-inch rotors. Also helping to bring the Expedition to a stop is electronic brake force distribution (EBD), which uses data measured by sensors to compare wheel speed 50 times during each rotation. If wheel lockup is imminent, the EBD system will redirect brake force. Another system called Brake Assist reads the speed and distance of brake-pedal travel. If the system detects that the driver intends to make a rapid stop, it will automatically boost hydraulic braking pressure.
Use of IRS in this new Expedition allows for a flatter floor, which means that the second- and third-row seats fold completely flat, maximizing cargo room. It also means that customers no longer have to remove the third-row seats and figure out where to put them when they want use of that rear cargo area. Instead, they just fold those seats into the floor. The upscale Eddie Bauer model will even feature a power folding option for the third row.
The choice of either a 4.6L V-8 or a 5.4L V-8 will power the new Expedition. The 4.6L V-8 features a new aluminum block and produces 232 horsepower at 4,750 rpm and 291 lb-ft of torque at 3,450 rpm. A more popular choice among Expedition buyers is the 5.4L V-8. This engine features a new cast-iron block designed to reduce vibration and noise. It produces 260 horsepower at 4,500 rpm and 350 lb-ft of torque at 2,500 rpm with 90 percent of that torque being available from 1,870 rpm to 4,280 rpm. In a further effort to supply a smooth and quiet ride, hydraulic engine mounts are used.
The 4R70W four-speed automatic transmission is one of the few pieces on the Expedition that wasn't significantly redesigned for '03. It uses a logic circuit to select the gear best suited for a particular driving situation. The circuit also has the ability to predict if the transmission will be able to carry the next gear. This helps to eliminate hunting between gears.
Sending power to the axles is the ControlTrac four-wheel-drive system, which also has received significant improvements. Managed by a dedicated electronic controller, the system gathers input from speed sensors on all four wheels and then adds data describing steering wheel position and throttle position to aid in determining how to transfer power front to rear. Previously the system only compared front and rear driveshaft speeds. ControlTrac also offers a two-wheel-drive mode for maximum fuel economy, and the ability to lock the transfer case in four-wheel drive in either high-range or a 2.62:1 low-range.
Another item designed to help the Expedition on loose surfaces is the AdvanceTrac electronic traction control system. It works by detecting wheelspin and then applying the brakes to stop the spinning wheel, transferring power to the wheel with traction. AdvanceTrac also has the ability to recognize when to reduce engine power to prevent wheelspin and when full engine power is needed, such as in sand.
So the Expedition has been significantly upgraded for '03. We have no doubt that it will provide a quiet, serene highway ride. But the big question is whether Ford has sacrificed off-highway ability to gain pavement prowess. Stay tuned: We intend to find out. When we do, we'll let you know.