The standard Premium Smooth Ride suspension in the 1500 soaks up large potholes and rough surfaces. The independent front suspension flattens the most rugged terrain, so passengers feel coddled, while the solid rear axle maximizes towing capability. Yukon XL boasts an impressive turning radius given its mammoth proportions, useful for crowded parking lots, U-turns, and off-road driving.

AutoRide is an optional suspension package that automatically varies shock damping according to driving conditions. Whether riding empty, carrying a full load of people, or towing a horse trailer, AutoRide continually adjusts the suspension for optimum ride and handling. This technology also helps reduce dive on braking (so that the nose of the vehicle doesn't dip down unduly) and body roll (lean) during cornering.

Towing a heavy trailer? A 1500 model is plenty for pulling a car trailer or a light boat trailer, but you may want to look at the 2500 models if you have a heavy load to pull and you pull it often. But the 2500 doesn't ride as well as the 1500. The rear suspension on the standard 1500-series models uses coil springs, while the heavy-duty 2500 models use leaf springs; coil springs filter road vibration much better and allow more precise suspension movements for better handling.

Quadrasteer ($1,995) gives the Yukon XL 2500 dramatically improved maneuverability in tight quarters. By turning the rear wheels opposite the direction of the front wheels, this four-wheel-steering system reduces the curb-to-curb turning diameter from the standard 44.3 feet to 36.5 feet. That's a huge difference when maneuvering in crowded parking lots and public garages, and it allows a U-turn in places that previously required backing up. Quadrasteer becomes even more important when towing trailers. It greatly improves control when backing, reducing trial and error. It also allows you to move a trailer into spots where you could not physically do so without it. It makes mere mortals look like professional semi drivers. Quadrasteer is well worth considering by anyone who frequently pulls trailers.

A 2500 with Quadrasteer isn't the smoothest vehicle on the road, however. We found its ride rough on I-405, a busy L.A. freeway with ripples that can set a stiff suspension to bouncing. Quadrasteer comes with heavier suspension components to support all of the extra equipment on the rear axle. Also, 2500 models come with light-truck tires, rather than passenger-car tires. Adding some heavy cargo would likely improve the ride, but we don't think we'd want to put up with the jounciness of the heavy-duty suspension on a daily basis unless we were towing at least once a month.

Responsiveness from each of the three available V8 engines is excellent. Most people will find the standard 5.3-liter V8 a great companion. The 6.0-liter V8 produces 325 horsepower in the 2500 and (with different cylinder heads) 335 horsepower in the Denali. Either way, it feels and sounds powerful when accelerating onto the freeway.

EPA fuel economy figures for 2005 weren't available at press time, but we'd expect the 5.3-liter Yukon XL to rate about 14/21 mpg with 2WD, 14/18 with 4WD. GMC said Yukon XL's 2005 fuel economy should be better than 2004's, thanks in part to new dual, 200-watt electric cooling fans that replace the engine-driven fan used previously. The electric fans are quieter, and a new radiator is more efficient, so GMC says we should also expect improved air conditioning performance when traffic comes to a standstill.

Yukon's transmission features a Tow/Haul mode that improves performance while towing through mountainous terrain. Pressing the Tow/Haul switch on the end of the gearshift lever changes the shift points of the automatic transmission. The Tow/Haul mode also lessens wear on the transmission by reducing heat buildup. It does this by holding the transmission in each gear longer before up-shifting, and then shifting up more abruptly to reduce the time the clutch packs have to slip and generate heat.

The brakes work very well, with easy modulation, good pedal feel, and good stopping power, even on heavy-duty 2500 models. A dynamic proportioning system continuously balances the front and rear brakes for maximum effectiveness. Hydroboost servo technology relies on hydraulic pressure rather than engine vacuum to reduce braking effort. Hydroboost brakes also require less pedal force during high-deceleration stops and improve pedal effort and feel during normal operation.

StabiliTrak is a valuable option that could save your life someday, or at least reduce your chance of stuffing your big Yukon XL into a ditch. StabiliTrak is an electronic stability control system that compares the driver's intended path with the vehicle's actual path, and adjusts engine torque and applies the brakes to any of the four individual wheels to help bring the vehicle back under control. Sophisticated sensors monitor the suspension, steering, antilock brake and traction control systems, constantly measuring steering angle, wheel speeds, brake pressure, lateral and longitudinal acceleration and yaw rate (the vehicle's rotation rate, such as when cornering). StabiliTrak comes standard on Denali but is also available on 2WD ($555) and 4WD ($750) base Yukon XL's. On 2005 models, StabiliTrak is combined with traction control and a limited-slip rear differential, all of which greatly improves the capability of 2WD models in slippery conditions. We highly recommend getting StabiliTrak.

Yukon XL 4WD models use a part-time four-wheel-drive system. (Just to make things confusing, GM calls this Autotrac.) Pressing a button switches the system to Auto 4WD, a mode that automatically shifts torque between the front and rear wheels as conditions demand; Auto 4WD works very well for most conditions we commonly encounter: wet pavement, gravel roads, or inconsistent conditions like snow, ice and slush. Shift into 4WD Hi when going into seriously slippery stuff or rugged terrain; 4WD Hi locks the front and rear axle speeds together for the traditional kind of four-wheel drive that is considered best for serious off-road driving. A 4WD Lo setting provides an ultra-low gear for creeping through deep sand, deep mud, deep snow or up or down steep grades. Shifting among the four-wheel-drive modes is as easy as turning on the radio, and is accomplished with four buttons mounted on the left side of the instrument panel.

Denali's full-time all-wheel-drive system requires no input from the driver whatsoever. It's a great system in inconsistent conditions (patches of snow and ice, gravel and pavement) because it automatically transfers power to the tires with the best traction.