Buick Rainier SUV brings choices in powertrains and traction

2007, Buick, Rainier SUV

VERDI, Nev. -- Bumping up a rutted path etched into eastern foothills of the Sierras west of Reno, we climb steadily into a barren landscape littered with sage and rock and sand. Although our sport-utility wagon -- Buick's mid-size Rainier -- has moved through 2,000 vertical feet of altitude gained since leaving Reno to the rearview mirror, a prudent driver, when viewing this slippery trail through the windshield, might naturally assume it should not be tackled without studded tires.

But we're steering Buick's largest SUV packed with powerful weapons for dicey motoring: A strong frame, big V8 muscle, all-wheel-drive (AWD) traction and a high-hitched chassis. It handles smooth pavement like the I-80 slab out of Reno with ease, thanks to an electronically-controlled air suspension working on the rear wheels to isolates any pavement bumps and deliver a comfortable ride.

Yet there's also the sophisticated AWD system aboard to keep the four tread patches planted firmly on pavement or sand and snow. The smart system brings push-button selections and automatic switching from standard rear-wheel-drive (RWD) traction to a mode that distributes engine torque between front and rear wheels.

Through a curve on sand our rear wheels began to slip out of line. In an instant, though, the AWD gizmo transfers torque seamlessly to the front tires, which claw for traction. In another instant those wayward rear wheels pull back into alignment and we proceed through the curve safely. It's a seamless transfer of traction accomplished so a driver can focus on steering without having to think about when to shift into four-wheeling mode.

If the system detects too much slippage, it locks into full-time four-wheel-drive (4WD), again without needing the driver's prompt. Also, every Rainier stocks the StabiliTrak vehicle skid control system as standard equipment. StabiliTrak helps a driver maintain control of the vehicle during quick steer-and-veer maneuvers or in slippery traction situations by employing various on-board sensors to measure Rainier's acceleration, deceleration, steering angle and yaw rate. The device automatically regulates the throttle or applies a brake to any wheel, if needed to check wheel spin.

And within the five-place cabin, Rainier the wagon reveals an impressive quality of quietness in terms of reducing noise, vibration and harshness (NVH). All external NVH is locked outside, the result of wrapping the compartment liberally with sound-deadening material, including thick layers of laminate applied to the windshield and front side windows. The effort to control NVH inside Rainier represents a sense of refinement more akin to a premium luxury car than a SUV riding on a truck's chassis.

Rainier skews toward the luxury side of motoring with plush seats in a cabin and deluxe appointments including rich leather upholstery. It comes with a choice of V6 or V8 powertrain in either RWD or the optional AWD traction. Rainier looks big but refined and decidedly like a Buick, due to a rounded prow that prominently displays the Buick signature of an oval grille in chrome inset with vertical bars and Buick's tri-shield insignia.

Headlamps protected behind clear lenses flank the oval grille and together form a bold horizontal band marking the face of the wagon, with a body-colored bumper running below and cradling round corner foglamps also in chrome. Side panels flare in arched wheelwells between door panels and contain big 17-inch aluminum wheels, while at the rear there's a large liftgate hinged at the top.

Rainier's agile nature and smooth ride quality are the result of a rigid ladder-frame chassis with one-piece steel rails running the length of the wagon. The unusual rails -- each a single piece of seamless tubular steel -- produce a foundation that's strong and light in weight using fewer component pieces.

An uncommon component is the rack and pinion steering mechanism coupled to hydraulic power assistance. It has a good on-center feel for steering with precise movements. For stopping, four disc brakes connect to an intelligent four-wheel anti-lock brake system (ABS), with electronic traction control (ETC) at the rear.

For locomotion, Rainier presents two choices. Standard engine is the in-line-six powerplant developed by General Motors to generate the high horsepower of a V8 but the fuel efficiency of a V6. The 4.2-liter six, with dual overhead cams and four valves for every cylinder, delivers 291 hp at 6000 rpm and a flat band of torque running to 277 lb-ft at 4800 rpm.

A heavy-duty Hydra-Matic 4L60-E four-speed automatic transmission mates with the Vortec 4200 straight-six to handle all of the torque. Optional power comes from a 5.3-liter V8 rigged with GM's Active Fuel Management (AFM) technology which cuts by half the number of cylinders engaged in the combustion process when boosted power is not needed in order to conserve fuel.

Big engines generally denote a dog-thirsty appetite for lapping up fuel, but the AFM mechanism is a real fuel-saver and turns Rainier into a rather efficient SUV. The plant generates big muscle -- 302 hp at 5200 rpm and 330 lb-ft at 4000 rpm -- yet earns respectable fuel-burn scores with EPA mileage estimates up to 22 mpg for RWD and 21 mpg with AWD. Despite the decent fuel economy ratings, Rainier's 5.3-liter V8 also gets high marks for towing a trailer, capping at a 6700-pound tow capacity for the RWD version.

In the cabin, Rainier provides a luxurious environment in monochromatic hues with personal comfort as the theme. A pair of form-fitting bucket seats in front stands beside a central console with multiple functions. It cradles the shift lever and a dash stack of gear for audio and climate systems, with twin air vents perched above.

Round analog gauges in the instruments cluster include a large tachometer to the left of the centered speedometer. A Tire Pressure Monitoring System (TPMS) goes to all 2007 issues, and there are new paint chips on the color chart, such as Midnight Blue Metallic or Graphite Metallic.

2007 Buick Rainier SUV $31,325

By Bob Plunkett

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