The Lexus GX 470: You Want Me To Drive This Where?
According to Kunihiro Hoshi, chief engineer for the GX 470: “Three of my top goals were to create a body-on-frame vehicle with sweeping off-road performance and unibody-like on-road capability, and, of course, it had to meet the Lexus quality standard.” He met his goals. But why would anyone want to bang this vehicle around on rocks?
#Toyota #Lexus #Suzuki
Whether you’ve been to the Park City, Utah, area or have come no closer than your TV screen during the 2002 Winter Olympics, you know that the Wasatch Mountains are readily described as majestic. They are also, well, mountains. Which means “high” for us flatlanders in Detroit and environs. When we were there this past summer with Lexus, the snow was gone; the cross-country skiing trails were bare, leaving the underlying rocks exposed. We were there to drive the new Lexus entry in the sport utility vehicle market, the GX 470.
One thing about this scenario: If the mountains are majestic, then the only way to describe what we were about to do is incongruous. Think about it. On the one hand, there is Lexus, known for the luxury sedans and coupes that have given the long-established American and European competitors a run for their money. Sure, there’s the Lexus LX 470, the Toyota Land Cruiser-based premium SUV, which, ostensibly, is a “go-anywhere” vehicle. After all, the Land Cruiser is well known for its capability. There is the RX 300, the unibody sport ute that is unlikely to go on any roads rougher than I-96 east of Telegraph. And now there’s something in the middle, the body-on-frame GX 470, that is more like its bigger brethren and is not that much smaller. (The GX 470 has a 109.8-in. wheelbase; an overall length of 188.2 in.; an overall width of 74 in. and an overall height of 73 in., while the LX 470 has a 112.2-in. wheelbase; an overall length of 192.5 in., an overall width of 76.4 in., and an overall height of 72.8 in.)
But on the other hand, this is a brand-new Lexus that we were about to take out on terrain that drivers of most vehicles wouldn’t even consider putting a vehicle on, certainly not one that is painted, say, Ash Blue Mica, and has standard ivory or gray leather trim seat facings, real maple wood trim on the dash, center console, and door panels, and a list of other standard features that is pages long. (To say nothing of the options like a 240-W Mark Levinson audio system; DVD navigation system, and DVD rear seat entertainment system—just to name a few.) Sure, one might put a bush beater out there, or a military-influenced four-wheeler, but a Lexus?!? (Denny Clements, Lexus Div. Group Vice President and General Manager: “While some SUV drivers might cringe at the thought of taking their truck off the highway, we’ve found that between 20% and 30% of luxury SUV owners expect to drive their vehicle off road.” And we suspect that a large percentage of them would do so only if they were lost.)
Apparently, the only one on the senior Lexus team who was enthusiastic about putting us out on trails like the one covered with sharp rocks with a propensity to eat tires was Kunihiro Hoshi, chief engineer for the vehicle, who knew that the GX 470 could handle the demands of the terrain.
And it can.
Still, this is a Lexus. It is being built in the Tahara Plant in Japan, along with the LS 430 and GS 430 sedans. Hoshi said that shortly after starting with Toyota, he was assigned to work with Ichiro Suzuki, the first Lexus chief engineer. “Suzuki-san understood the spirit of Lexus. He is a well-respected engineer who knew what it would take to build a quality, luxury vehicle that could compete right out of the box with such historic marques as Mercedes Benz and BMW.” Which, arguably, Lexus has done. And speaking of those two other marques, it is worth noting that Hoshi and his colleagues benchmarked the Mercedes ML500 and BMW X5 4.4i during the development of the GX 470.
The base of this vehicle is a chassis that consists of full-length box-section frame rails with nine welded cross members. There’s a double wishbone front suspension with coil-over shocks. The shock absorbers are vertically oriented, not on an angle, thereby improving ride comfort (helping meet the goals of good on- and off-road feel). The rear suspension is not independent, as some of the other SUV manufacturers seem to be going for. It has a solid axle and a four-link setup. Instead of coil springs, however, it is fitted with air-filled reinforced rubber springs. (The air suspension permits manual selection of Hi Mode for off-roading or Lo Mode to load the caviar and other groceries) The vehicle is also equipped with the Lexus Adaptive Variable Suspension system, that manages all four shocks independently so as to meet the selected characteristics of the four selectable settings (ranging from Comfort to Sport).
The steering is variable-gear rack and pinion. The brakes are four-channel, four-sensor ABS. The brakes are tied into the vehicle’s A-TRAC, or Active Traction Control, system, which works with the Torsen, or torque-sensing, limited slip center differential. This means that if a wheel sensor—and magnetic resonance elastography sensors are used, which means that the wheel speed sensors can read forward and reverse rotation, not just forward, as the more common static, or inductive, sensors can—determines that a wheel is slipping, brake pressure is applied so that torque is diverted to the opposite wheel on the same axle. If both front or both rear wheels are slipping, then the Torsen diff changes the torque split between the axles. Typically, the full-time four-wheel drive system provides a power split of 40% front/60% rear.
Also in the arena of electronic assists, there are the Hill-start Assist Control (HAC) and the Downhill Assist Control (DAC) systems that are also found on the GX 470’s platform-mate, the Toyota 4Runner. HAC keeps the vehicle in place for a few seconds while the driver attempting to go up a steep grade moves his or her* foot from the brake to the accelerator. DAC requires the driver to put the shifter in low, the transfer in Low-4 and take his or her feet off the pedals; it then uses the braking system to keep the vehicle going no more than 4 mph downhill.
“In reality, you might say the GX 470 is a baby brother to the LX 470,” said Clements. Part of the genetic material that the two share is found under the hood, in the form of the double-overhead cam, 4.7-liter 32-valve V8 that produces 235 hp @ 4,800 rpm and 320 ft-lb of torque @ 3,400 rpm. Because some owners might opt for the optional tow package, the engine produces 80% of its peak torque (i.e., 256 lb-ft) at 1,100 rpm. And both vehicles have the same five-speed, electronically controlled automatic transmission.
According to Denny Clements, the goal is to sell 20,000 GX 470s per year. Months before the vehicle was available, 5,000 were presold. And we’re betting that the on-road manners of the vehicles will be those that are most appreciated. But not because the GX 470 can’t go off road—way off.
*Probably “he”: “We expect GX owners to be 50 to 60% make, 40 to 50 years old, 75 to 85% married, and 65 to 75% to be college educated.”—Denny Clements.
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