Hummer H1 Alpha

The "Alpha" was an extensively re-engineered H1 that was equipped with GM's Duramax Diesel and 5-speed Allison transmission. The previous turbo-diesel engine suffered from sluggish sales; lack of power was one of the reasons for customer resistance. In 2002, AM General CEO Jim Armour took the idea of repowering the H1 to Bob Lutz and the GM Luxury Vehicle committee. GM soon approved the use of their Duramax/Allison powertrain for the H1. This would support the continuation of the H1; it would also represent an updating in terms of power, torque, refinement and the ability to meet 2004 heavy duty EPA emissions requirements.
The update program commenced in late 2002 with production launch slated to be fall of 2004. The engineering team chose the engine variant out of the GMT560 truck (the C4500) because it packaged better into the H1 engine bay; however, 23 engine component changes were required and the team had to do a 2.0 in (51 mm) body lift to accommodate the taller engine and its turbo housing (a prior 0.5 in (13 mm) lift had been done for MY96 to accommodate the turbo on the 6.5L engine). The 8th digit of the VIN number is 3, setting this version of the 6.6L Duramax apart from the versions used in pickup trucks. The GMT560 engine calibration was used with minimal modification; engine output was 300 hp (220 kW) and 520 lb⋅ft (705 N⋅m) of torque. The Duramax engine was equipped with cooled exhaust gas recirculation and an internal engine oil cooler, thus, requiring a 40 percent heat rejection increase to engine coolant. Because space was limited between the air-lift brackets that protrude from the hood, the fan system was modified by putting it directly under the coolpack and driving it through a special gearbox directly off the crankshaft damper pulley. Several other cooling system modifications were required to assist with cold starting from −30 °F (−34 °C).
Other major modifications included the use of special high-strength steel in the chassis frame, a more powerful steering gear; quieter axle differentials, redesign of the geared hubs to use quieter helical gears, new induction, exhaust and electrical power systems; and re-engineering of the fuel supply and filtration system.
The Duramax engine delivered more torque at lower engine speeds than the 6.5L, combined with a lower gearing ratio (about 44.5 to 1 in low lock) made the vehicle more powerful. Other changes included centralized tire inflation and a new interior.
Production launch was early in 2005, and continued until production ceased in mid-2006. All vehicles built during this time are classified as model year 2006 (10th digit in VIN is a 6.)
The program was cancelled May 12, 2006 because GM decided to withdraw technical and financial support for future engineering and recertification.