The 5.3-liter V8 provided plenty of power for the extended cab SLE models we drove and the 6.0-liter V8 was more than enough for the SLT Crew Cab we checked out. All engines need to be revved up (by truck standards) for best grunt. Generally the Sierra models match competitors for smoothness, though by benefit of their five-speed automatics the Ram 4.7 typically runs with GM's 5.3, the Ram 5.7 and Titan 5.6 compete with the GM 6.0, while Tundra's 5.7 and six-speed auto performance can be matched only by the Denali's 6.2 and six-speed auto.

Of the suspensions, the Z83 is claimed the smoothest ride while the Z85 is slightly stiffer and for those who often tow moderate trailers. The Z71 is set up to enhance off-pavement driving. The Z60 configuration is for what GMC calls maximum street performance and includes big 20-inch wheels. The NHT package is designed for Sierra owners who need to tow and carry the heaviest loads.

With NHT, the SLT Crew Cab 4x2 is equipped with the Vortec Max 6.0-liter V8 engine, and a 3.73:1 rear axle. It was fitted with StabiliTrak, side-curtain airbags, a locking rear differential, and a convenience package that includes adjustable pedals, remote vehicle starting system and rear park assist. The SLT with NHT suspension is designed for maximum capacity trailer towing, with a special steering gear, shock absorbers, rear axle and tires.

The suspension is compliant relative to its carrying capacity but if you drive empty and don't tow you don't want to get the NHT package just so you can have the 6-liter V8 due to the harsher ride. Isolation and control are both very good but the best suspension setup for comfort on the widest range of surfaces is typically the Z71 package.

By virtue of its fairly stiff spring and shock rates, the NHT suspension can be driven aggressively on winding roads with tire squeal the primary indication you're approaching limits. Steering is direct by truck standards and nicely weighted, providing good feedback about how hard everything is working though the assist can fall behind during repeated full-lock maneuvering as when backing a trailer.

All new Sierras benefit from much improved brakes over earlier models, whether they have the rear discs or drum brakes.

For 2008, drivers who tow will appreciate the optional integrated brake controller like that used on the Sierra HD. However, be sure your trailer brakes are compatible with it before choosing the option, as some electro-hydraulic disc conversions do not work with the integrated controller.

The highest tow rating is 10,500 pounds on extended cab (not long bed) or crew cab models; top regular cab rating is 8900 pounds. Note these figures typically apply to a truck with just a driver on board, and vary substantially based on a variety of equipment and options.