From Peterson's : David Kennedy: Was off in Detroit at General Motor's Milford Proving grounds to see the newest GM engines and transmissions. He drove 2006 Silverado 2500HDs with the new 6.6L (LBZ code) Duramax (360 hp / 650lb-ft of torque) backed by the newly upgraded Allison 1000 now with six speeds! He also spied a sneak peak of a light duty 3/4-ton with a 4.9L Duramax V6 backed by a 4L80E. No word on when we might see this engine in production - but now we know it exists. David also got his first chance to drive a Hummer H1 (Duramax/Allison 6-speed version) after being at the magazine for five years. He had to keep it on the pavement, and can now say no matter how cool you think these trucks look on the street - they're no fun to drive on the pavement. It's just too cramped inside!