M998 HMMWV: Description
This is my second ex-military truck. It's an M998 High-Mobility Multipurpose Wheeled Vehicle, commonly called a HMMWV (pronounced "humvee"). This 1-1/4 ton truck replaced several different 3/4 to 1-1/4 ton trucks in use at the time of its introduction. There are many variations of this truck, including lightly-armored weapon carriers with machine guns, grenade launchers or TOW missile launchers, ambulances, communication shelter carriers, etc. There have also been other custom configurations based on the HMMWV chassis, such as the Avenger missile system. There are civilian versions of the HMMWV, called "Hummers". My truck was used by the US Marine Corps before I bought it.
The HMMWV has been a fairly controversial truck. Every opinion I have heard about them has been either strongly positive or strongly negative. It has been criticized for being too heavy, too wide, to unreliable and to complicated. It has also been praised for being extremely maneuverable, very easy to drive, being very capable on extremely rough terrain, and being very reliable (go figure!).
At 7'1" wide, the HMMWV is much wider than the M151 Mutt which it replaced (among other trucks). It has a very high ground clearance of 16" under the axles, and its width helps compensate for its high center of gravity. The entire driveline is mounted very high in the body of the truck; in fact, the truck is somewhat cramped inside despite its width, because part of the engine lives between the front seats! It has 4-wheel independent suspension and full-time 4-wheel drive. Ground clearance is improved by geared hubs in each wheel, which allows the axles to enter the hubs above the centerlines of the wheels. The differentials are mounted even higher, creating the appearance of a cavernous tunnel underneath the truck. The 4-wheel disc brakes are mounted inboard at the differentials. The truck has a characteristic "sloshy" feeling when stopping because each brake are separated from its wheel by a gearbox and a driveshaft.
Although it's a wide and heavy vehicle, the HMMWV is very easy to drive. It's curb-to-curb turning diameter is about 11' narrower than my 1992 Toyota 4Runner's, allowing it to maneuver around obstacles much more easily than you would expect from a truck of its size. It has an automatic transmission and power steering. The power steering applies a lot of steering boost, allowing the driver to make tight stop-to-stop turns with a finger or two, even though the truck's steering wheel is quite small. The sloshy feeling of the brakes takes a bit of time to get used to, but the truck is still a joy to drive right from the start.