The original High-Mobility Multipurpose Wheeled Vehicles (HMMWV) was the M998. In 1991, the M1097 was developed to fill the need for a vehicle with a higher payload and towed-load rating than was provided by the earlier models. This heavy Humvee has a reinforced frame, heavier springs, tires and rims and other improvements. It is powered by a 190 horsepower turbo supercharged version of the diesel engine, and like the rest of the HMMWV family, the M1097 features full time four-wheel drive and automatic transmission.
Broadened demands placed on the chassis type resulted in a series of increases in the vehicles’ gross vehicle weight rating, along with associated improvements in the drive train. These changes culminated with the expanded capacity variant (ECV), sometimes also known as the Expanded Capacity Humvee (ECH) was developed.
The ECH vehicles added a turbosupercharger to the 6.5 liter V-8 diesel engine, improved differentials, brakes, cooling system, and has a beefier frame. The ECH vehicles include the M1113 base vehicle, M1151 armament carrier, M1152 cargo and troop carrier.
As of 2006, the M1113 became the base vehicle for future HMMWV orders, with the bulk of these consisting of M1151 and M1152 variants.