The major portion of our long-term 2500HD's option load was occupied by the $4810 6.6-liter Duramax turbodiesel and $1200 Allison five-speed heavy-duty automatic transmission. A $240 tonneau cover, $285 locking rear differential, $190 trailering package, and $95 skidplate package rounded out the Silverado's equipment tally, totalling $41,705.

From the get-go, editors commented on how substantial the Silverado HD felt, attributable to the large-section, fully boxed ladder frame with hydroformed front section. But much of that "all of one piece" feel came from the strong Duramax motor. This 6.6-liter turbodiesel was designed and developed by diesel-expert and General Motors partner Isuzu Motors. The Duramax employs the latest in diesel technology, including highly efficient, low-emissions direct injection with a high-pressure common rail. Lightweight aluminum heads with four valves per cylinder facilitate top-end breathing, and a cast-aluminum sump and ribbed cast-iron block reduce noise/vibration/harshness. Charge-air cooling promotes turbocharger efficiency by increasing the density of the intake air. An electronic throttle eliminates any direct noise path from the engine to the cabin. The result is near-Viper-like gobs of grunt (520 lb-ft at 1800 rpm), more than ample to coax a 5631-pound truck to speed. Senior Road Test Editor Chris Walton effused, "It amazes me how quick this truck is, as it does other drivers who hear the diesel and assume they'll beat it from the stop sign--not!" Added Executive Editor Matt Stone, "Man, what a torque curve. The mid-range passing acceleration offers confidence not many diesels can match."

The other player in this dynamic drivetrain duo is the Allison 1000-series automatic transmission. This gearbox, normally associated with medium-duty big rigs, offers electronic shift-timing control and quiet-running helical planetary gearsets. There are two operating modes, normal and Tow/Haul. In the latter mode, the transmission will automatically downshift every time the driver taps the brakes when descending long, steep grades--a big help when hauling heavy loads. Stone concluded, "The Allison automatic deserves the Nobel Prize for greatness in the truck-transmission category."

Heavy-duty pickups need heavy-duty springs to carry heavy-duty loads, and here the laws of physics catch up with reality. Many freeways and interstates are paved with concrete, and, in time, the sections buckle and warp due to heating and cooling cycles. When the 2500HD drives over these sections at freeway speeds, say 65 to 75 mph, the combination of a long wheelbase and undulating road surface sets up a sine-wave vertical oscillation in the cab that'll have your gizzard playing ping-pong with your gullet. The only alternatives are throwing considerable ballast into the bed, slowing down to obstructionist speeds, or finding another route. On normal roads, the ride quality is palpable. With a load, the 2500HD comes into its own. In a towing test with a 5000-pound boat, Senior Feature Editor Scott Mead noted, "The extra 275 pounds of tongue weight helped smooth the ride."