General Motors Fires Salvo in the 2006 Torque Wars

It's no secret that diesel powerplants dominate heavy-duty pickup trucks. Even in those cases where they aren't the top-selling engine, it's frequently a question of availability, not satisfaction or pricing. So, while the new HD GM pickups are still a couple of years away, an upgraded Duramax/Allison combination will be available for 2006.

D-Max Plus D-6
Regardless of application, a diesel combined with an Allison automatic tends to produce a match made in motoring heaven. Duramax and Allison engineers are quick to praise the others' product and note the synergism involved in joining the two, so this most popular combo was thoroughly gone through for 2006; note that manual-gearbox versions of the Duramax retain their 2005 ratings.

Vortec 6200 V-8

Getting more power out of a diesel is relatively simple; doing so cleanly and reliably is another story. The 2006 Duramax LBZ has been upgraded with thicker cylinder-head decks, a stronger bottom end, and larger cooling capacities to handle the added loading. The power comes from aero improvements to the variable-geometry turbo and intake plumbing, five-pulse-per-stroke injection using higher 26,000-psi pressures, a lower compression ratio of 16.8:1 (down from 17.5:1) to allow for lower cylinder pressure and better combustion control, and the inevitable electronics reprogramming. In addition to the extra power, the engine revs 200 rpm higher, gets better fuel economy, and is quieter. It now seems like the ECM-controlled starter is noisier than engine idle. The glow plugs also have been revised and an intake air-grid heater was added.

Duramax 6600 HD and six-speed

Backing up the 360-horsepower Duramax is the newest 1000-series Allison automatic, now a six-speed unit with a second overdrive. It, too, has seen strengthening through bigger clutch-pack capacity, noise reduction good for a 71-percent drop in dBA in first gear, and a 32-bit controller for more accurate control. The grade-braking feature now works with cruise control, so on those milder grades where you leave the cruise on, the transmission will select gears to maintain a desired speed. General weight and tow ratings remain the same as those of the 2005 models, since the basic truck architecture is unchanged.