• The Chevy TrailBlazer EXT is the extended version of the TrailBlazer, one of among the best of the truck-based midsize SUVs. It's capable of hauling heavy loads and negotiating rugged off-road terrain while also remaining smooth, comfortable and civilized.
• The long-wheelbase TrailBlazer EXT is available in two trims, the LS and LT. Both are stretched 16 inches between the front and rear wheels to provide a third row of seats for seven-passenger capacity and more cargo room. A four-wheel drive option is available on all models. The TrailBlazer EXT LS and TrailBlazer EXT LT are equipped similarly to their standard-wheelbase counterparts. The EXT LS models come standard with a HomeLink transmitter, fog lamps, 17-inch wheels, and other upgrades. The Vortec 5300 5.3-liter V8 which powers the vehicle delivers 300-horsepower and 330 pound-feet of torque. All EXT models come standard with a four-speed automatic transmission.
• For 2005, the Vortec 5300 V8 with its Displacement on Demand technology promises about 8 percent better fuel economy than the engine it replaces.

An extended-wheelbase model called the TrailBlazer EXT adds three-row seating, accomodating up to seven people. It comes standard with the same excellent six-cylinder engine, but a new V8 is also available.

New for 2005, the Vortec 5300 V8 with its Displacement on Demand technology promises about 8 percent better fuel economy than the engine it replaces. Equipped with the V8, a 2WD Trailblazer EXT can tow up to 7,000 pounds. The EXT needs the V8 due to its heavier weight, and because of its much greater length, the EXT lacks the handling and stability that make the standard TrailBlazer such a great family vehicle.

Curtain side-impact airbags with a rollover sensing system designed to provide increased head protection are available on 2005 models. Also new is an occupant-sensing system for the front passenger-side airbag. There are also improved seats, refinements to the navigation system and more bright trim for the interior.

Overall, TrailBlazer looks sturdy and neat, with confident lines that express utility. The pillars and window lines are graceful, while the big fender flares are visually bold. At the rear is a convenient step in the center of the bumper. But the stacked round taillights look lumpy and googly-eyed.

The track (the distance between the left and right tires) is the widest in the class, 2.2 inches wider than the Ford Explorer in front and nearly an inch wider in the rear. This gives the TrailBlazer more hip and shoulder room.

The easiest way to tell the TrailBlazer from the TrailBlazer EXT is to look at the rear passenger doors; they're full-size doors on the EXT but the rear wheel wells cut into them on the standard-length model. The seven-seat TrailBlazer EXT is 16 inches longer in wheelbase than the standard five-seat TrailBlazer and looks disproportianately long and narrow.

Called the Vortec 4200, the 4.2-liter inline-6 features dual overhead camshafts, four valves per cylinder, and variable phasing of the exhaust cam. It's rated 275 horsepower and 275 pound-feet of torque. (Torque is that force that thrusts you off the line and up steep hills.) Ninety percent of the peak torque is available at just 1600 rpm and it's still there at 5600 rpm. The engine is still striding, not screaming, when the full-throttle upshift comes at 6000 rpm. That torque gave us confident power when attempting passes on steep uphill two-lanes. It offers strong acceleration without forcing the transmission to downshift. The four-speed automatic transmission is programmed well and makes a good companion for the engine. Shifts are smooth.

Towing was a high priority in the TrailBlazer's engineering. Six-cylinder models are rated to tow 6300 pounds with 2WD, 6100 with 4WD. The six-cylinder engine is designed to run cool while towing, thanks in part to a big seven-quart oil pan.

Big ventilated disc brakes provide stopping power, and four-wheel ABS is standard. Under hard braking, the nose didn't dive, keeping the TrailBlazer remarkably level and stable.

We found the ride excellent, very smooth without being too soft. The TrailBlazer was designed to lean up to 5 degrees in corners, and then stop leaning. It features a wide track and low engine position, which drops the center of gravity. A vehicle with a low center of gravity is generally less likely to roll over than a vehicle with a high center of gravity. TrailBlazer has a very tight turning circle of 36.4 feet, because the suspension and engine design allow for large steering angles.

The chassis and suspension are highly developed with design features normally associated with sports cars: rack-and-pinion steering, four-wheel vented disc brakes with twin-piston calipers in front, independent front suspension with short/long control arms, live rear axle using five-link location with Bilstein gas-charged shock absorbers and coil springs, and thick antiroll bars front and rear. TrailBlazer's chief designer had previously worked on the Camaro and Firebird and his approach was to put some 'sport' in this sport utility. The chassis rails are shaped by hydroforming, which makes them stronger and lighter. No less than eight crossmembers contribute to TrailBlazer's torsional rigidity, and there are 12 tuned body mounts that use rubber pads and hydrualics to dampen vibrations.

Leaving the highway for the dirt, we found the TrailBlazer impressively stable on washboard surfaces. It bottomed on dips, however, signaling that the optional skid plates ($130) are necessary for off-road driving. When equipped with the 17-inch on/off-road tires and skid plates, the TrailBlazer easily chugged along at 5 mph through soft sand in Auto4WD.

Four-wheel-drive TrailBlazers feature GM's Autotrac system, which offers four settings: 2WD, Auto4WD, 4HI and 4LO. Switching in and out of 4WD can be done on the fly with a flip of a switch. The transmission must be in neutral to engage or disengage 4LO. In Auto4WD, power is shifted to all four wheels as conditions require. The TrailBlazer can be towed in the Auto mode without having to disconnect the driveshaft, a convenient feature. Traction control ($195) is available for 2WD TrailBlazers.

As impressed as we were with the TrailBlazer, we were less than enchanted by the TrailBlazer EXT. The long-wheelbase EXT lacks the responsiveness and stable handling of the standard TrailBlazer. The EXT feels long and narrow. That's not surprising, given that the TrailBlazer EXT is longer.

The standard TrailBlazer seats five passengers, while the TrailBlazer EXT seats seven. Second-row space is nearly identical between TrailBlazer and TrailBlazer EXT. Both offer more room in the second row than the Ford Explorer, particularly hip room.

Cargo space in the EXT is generous. Fold the second- and third-row seats and TrailBlazer EXT offers 107 cubic feet of packing room, more than the standard TrailBlazer (80), Ford Explorer (81), and comparable to the full-size Chevrolet Tahoe (105). The cargo floor isn't as flat as we'd like, though, and a gap between the two third-row seats makes it less dog-friendly.

The Explorer, however, provides a bit more third-row people room than the TrailBlazer EXT. Head, hip, and leg room in the Explorer's third row measure 38.9, 45.4, and 34.9 inches, respectively. The corresponding numbers for the TrailBlazer EXT are 38.1, 49.2, and 31.2. TrailBlazer EXT is 2.6 inches wider than Explorer, which accounts for the additional hip room. But clearly, the Explorer's independent rear suspension, and resulting low floor, allowed Ford to pack more leg room and head room into a significantly shorter wheelbase.

All TrailBlazers feature complete and clean instrumentation. A big tachometer is on the left, speedometer in center, and on the right are smaller gauges for water, battery, gas and oil. Optional on the four-spoke, leather-wrapped steering wheel are eight buttons for climate, sound, cruise control and a driver information center. Heating and air conditioning can be controlled separately by the driver and front-seat passenger. EXT models add separate climate controls for rear-seat passengers as well. Interior lights abound, including reading lights.

The center console includes an open storage bin, an enclosed compartment and two cup holders forward of the gear lever plus two cup holders for the rear passengers. There are pockets in the front doors and behind the front seats, though none in the rear doors. Behind the rear seat is a small hidden compartment under the floor, while optional features include a cargo net, scrolling tonneau cover and power outlet. An overhead console on the LT includes a sunglasses holder plus Travelnote digital recorder.

Head-curtain side-impact airbags ($495) unfold from the roof rail between the A-pillar and side window header. When the bag deploys in a moderate-to-severe side impact, it is angled somewhat toward the window to help provide protection for front and rear-seat outboard passengers. The new system replaces the previous seat-mounted system, which protected the driver and front-seat passenger only. TrailBlazers equipped with head-curtain airbags also feature a new rollover sensing system that triggers both the side-curtain airbags and safety belt pretensioners. The rollover-sensing module uses a complex algorithm based on lateral and vertical accelerations, roll rate and vehicle speed to determine whether to deploy the safety systems. Standard on the 2005 TrailBlazer is GM's Passenger Sensing System (PSS), which can deactivate the front-passenger airbag if it senses an unoccupied front passenger seat or the presence of a smaller occupant. A status indicator on the instrument panel alerts occupants that the passenger airbag is on or off. Even with this system, however, we strongly recommend carrying under-age passengers in an appropriate child seat placed in the second.

Smooth, stable, and powerful, TrailBlazer works well around town, on the open highway, and in the back country. Almost none of that applies to the long-wheelbase TrailBlazer EXT, however, which surrenders much of the standard model's ride and handling for third-row seating capacity.

New Car Test Drive correspondent Sam Moses reports from the Columbia River Gorge, with Mitch McCullough reporting from Los Angeles.