The standard Premium Smooth Ride suspension in the 1500 models soaks up large potholes and rough terrain. The independent front suspension flattens the most rugged terrain, so passengers feel coddled, while the solid rear axle allows impressive 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.

Quadrasteer muddies this pleasant picture. A Yukon XL 2500 with Quadrasteer delivered a rough ride on I-405, a rippled, bumpy highway in Los Angeles. Quadrasteer requires 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 needed to tow heavy trailers. (Conversely, we enjoyed a much more pleasant ride from a GMC Sierra Denali pickup with Quadrasteer.)

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 that comes on the Denali and heavy-duty 2500 models feels and sounds powerful when accelerating onto the freeway.

The transmission features a Tow/Haul mode that improves performance while towing through mountainous terrain. Pressing a 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 heat buildup.

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. The brake system was upgraded for 2003 for improved performance and pedal feel. For 2004, the system was further upgraded for improved performance in high-deceleration stops, and improved anti-lock performance; this new Hydroboost system relies on hydraulic pressure rather than engine vacuum to reduce braking pressure. Hyrdoboost 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 anti-skid 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 rotation rate, such as when cornering).

Yukon XL 4WD models use a part-time four-wheel-drive system GM calls Autotrac. Shift Autotrac into 4WD Hi, and it 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. However, pressing a button switches the system to an Auto 4WD mode that automatically shifts torque between the front and rear wheels as conditions demand, an arrangement that's good for wet pavement, gravel roads, or inconsistent conditions. A 4WD Lo setting provides an ultra-low gear for creeping through deep sand, deep mud, deep snow or up or down steep grades. Autotrac was revised for 2003 for more fuel-efficient operation in 2WD mode, and for improved feel in the Auto mode when turning corners at low speeds. 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.

A locking rear differential is optional, and a good idea for heavy snow or serious off-road driving.

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

Towing a really 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. On the other hand, the 1500 model comes with torsion bars up front and coil springs in the rear, which filter road vibration much better than leaf springs in the rear of the 2500 model.

Quadrasteer ($1,995) gives the Yukon XL 2500 vastly 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, an improvement of about 20 percent. 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, eliminating trial and error runs. It also allows you to move a trailer into spots where you could not physically do so without it. It's well worth considering by anyone who frequently pulls trailers.