The optional 4.7-liter V8, introduced for 2005, represents a huge improvement over the V8 it replaced. We found it delivered strong performance for our 2006 4Runner. It's smooth and tractable and never struggles when thrust is needed. The V8 features variable valve timing with intelligence (VVT-i) and electronic throttle control with intelligence (ETCS-i), turning it into a real performer. It's rated 260 horsepower and 306 pound-feet of torque, and adds about 190 pounds to the weight of the vehicle. EPA fuel-use estimates are 16/20 mpg for the 2WD V8 and 15/19 with 4WD. Toyota recommends premium fuel. Both engines feature a cranking system that keeps the starter engaged until complete combustion is achieved, freeing the driver from holding the key until the engine turns over. This is a feature usually associated with expensive luxury sedans.

Both engines are paired with a sophisticated five-speed automatic transmission. More gears means better response for any given situation along with better efficiency. The transmission is equipped with Artificial Intelligence Shift control, which changes gear-shifting patterns according to driving conditions and driver intent. It works well and seems to understand when you want to cruise and when you want to get with the program, and it shifts smoothly around town.

The 4Runner handles very well for a truck with a live rear axle. We drove all the models over twisting back roads along the Oregon coast and found them easy to drive at a quick clip. We also spent a lot of time in a 2006 Limited 4WD V8 around Los Angeles. The suspension damping is excellent. When the road got bumpy, we could tell our truck had a solid rear axle rather than an independent rear suspension, but the 4Runner still handles more confidently than other live-axle SUVs, such as the Chevy TrailBlazer. Rack-and-pinion steering gives the 4Runner quick response and good steering feel.

The ride on unpaved roads is smooth, which is important on long gravel treks over washboard surfaces. The 4Runner's well-tuned damping and progressive-rate spring bumpers are to thank here. Where the 4Runner really comes into its own, however, is when the terrain gets truly gnarly. There's lots of suspension articulation for climbing over boulders and gullies, and a host of technology for handling steep, slippery grades.

Still, the 4Runner is a truck, not a car. Rather than using unit-body construction like the Toyota Highlander and RAV4, the 4Runner is built on a separate ladder frame that features full-length box-section frame rails. Toyota also steered away from using an independent rear suspension like the one on the ladder-frame Ford Explorer. An independent rear suspension would have offered better ride quality and allowed for a roomier interior, but Toyota said off-road capability was a high priority for the 4Runner and that its live rear axle provides more suspension travel.

A limited-slip differential, optional on many SUVs, is standard on even 2WD 4Runners. We found the two-wheel-drive models impressively capable on rugged terrain; indeed, a 2WD 4Runner is more capable off road than many all-wheel-drive SUVs. For ultimate traction, however, you do need a four-wheel-drive model; and it seems to us that if you don't need four-wheel drive, then perhaps you should not be looking at 4Runners though it is a good highway vehicle.

V6 4WD 4Runners are equipped with Toyota's Multi-Mode shift-on-the-fly system, which incorporates both a two-speed transfer case and a Torsen-type limited-slip center differential. The driver can shift between 2WD, 4WD High, and 4WD Low. The Torsen center differential allows the use of 4WD High in all types of driving conditions, and on all types of roads, from dry to wet to snow-covered. The system gives the 4Runner a sure-footed feel because power is applied to all four wheels. But the center diff can also be locked out for military-truck-grade traction in extreme slop.

4Runners with the V8 and 4WD come with what Toyota calls a full-time system, but it operates much less like a car or crossover-style all-wheel-drive than it does Toyota's own part-time system with the 2WD mode removed. A Torsen center differential distributes torque 40 percent front / 60 percent rear under most conditions and changes the ratio as needed based on steering input and wheel slip. It automatically shifts to 29/71 front/rear during steering maneuvers to enhance tracking through the curve. If the rear wheels should spin, however, the center differential can shift the ratio to 53/47 to control the slippage. And again, it can be locked out completely when the going gets extreme.

All 4WD 4Runners come with Toyota's Downhill Assist Control (DAC) system, which controls the speed when creeping down steep, slimy grades. Shift into 4WD Low, check to make sure DAC is activated, pull to the edge of the nearest precipice, take your feet off the pedals, and steer your way slowly down the trail. Once you make the leap of faith that comes with allowing the machinery to do the work for you, Downhill Assist works very well and is easy to manage. The antilock brakes make a noisy "dunk, dunk, dunk" sound as the system lowers the 4Runner safely down the slippery slope. Gently touch the gas or brake pedals to slow or speed your progress, then take your feet off the pedals again, and the system comes back on: "dunk, dunk, dunk, dunk." DAC helps keep the 4Runner pointed in the direction you steer it, using ABS to curb the tendency for the vehicle to get sideways on steep descents. The system will work continuously for three minutes (because the brakes will heat up with prolonged use), but Toyota officials say it only needs the shortest of breaks to continue. Three minutes is usually more than enough time to get to the bottom of the sort of extreme descent we're contemplating here.

All 4Runners, 2WD and 4WD, come with Hill-start Assist Control (HAC), which is designed to prevent the vehicle from rolling backward or slipping sideways when starting off on a steep ascent. The system uses the brakes to stop an individual wheel or all wheels, whatever it takes to keep 4Runner running forward.

The optional rear air suspension offers improved ride and performance when towing or hauling heavy loads. The air suspension automatically adjusts the ride height according to vehicle load. The driver can also manually raise the rear suspension when driving off road to increase the ground clearance and improve the rear departure angle. This latter feature is useful in the extreme conditions, but most owners will never go there.

X-REAS improves handling dynamics on the road with no compromise in off-road articulation or travel. X-REAS reduces the tendency of the vehicle to bob up and down in corners and improves handling by damping body pitch and roll. A simple system, it links the shock absorbers diagonally through hydraulic lines (e.g., the front left shock is linked to the rear right shock). A central control damper helps keep the system in balance.

Anti-lock brakes (ABS) with Brake Assist and electronic brake-force distribution (EBD) come standard on all 4Runners. The four-channel ABS prevents the wheels from locking under severe braking, improving driver control. The 4Runner's ABS uses an off-road algorithm to improve stopping performance in slippery conditions, a great feature. EBD automatically balances the braking force front-to-rear for shorter stopping distances. Brake Assist helps a driver who may not be pressing the brake pedal hard enough during an emergency stopping situation by maximizing braking power regardless of the force on the pedal.

Overall, we found that 4Runner's brakes worked well. They felt a bit sensitive on the V8 models, and were a little challenging to modulate for limo-smooth stops, but owners will quickly adjust to this.

The 4Runner's fuel tank was specifically designed for off-road use. The tank is plastic, offering better protection against corrosion, rust-through and connection leaks. Yet the plastic tank is armored by a steel case for protection against debris kicked up by the tires, or against the rocks off-highway enthusiasts might encounter.