For many readers of Military Vehicle Magazine, owning an historic military vehicle (HMV) is a hobby. While a hobby doesn’t have to have a practical purpose, when it comes to vehicular hobbies, one should probably consider some practicalities when choosing a vehicle—most notably how much the vehicle is going to cost in both time and money versus the enjoyment it brings. There is no practicality in buying a vehicle that is too large, too small, or otherwise unsuited to whatever you hope to do with it, or a vehicle that requires more maintenance and upkeep than you’re willing or able to give it. With large numbers of HMMWVs currently being released from U.S. military service, you may be considering one as a hobby project, so the purpose of this three-part article is to drop a little knowledge to help you decide if you really want a HMMWV—and are willing and able to give it the time and attention it needs.
BASIC HMMWV HISTORY
We’ll start with this basic HMMWV History; and it may be worth noting that while HMMWVs were sometimes called “Hummers” by GIs early in their service years, today that term is generally used for the civilian H1, H2, and H3 versions and the common military nickname is “Humvee.”
World War Two might be described as vehicular war, a war in which ground mobility—transporting troops and supplies quickly and efficiently—proved a major factor in victories. General Dwight D. Eisenhower said, “The equipment most vital to our success in Africa and Europe was the bulldozer, the jeep, the 2-1/2 ton truck, and the C-47 airplane. Curiously, none of these were designed for combat.” It should also be noted that three of these pieces of vital equipment were vehicles.
After WWII, the U.S. military set about developing a new fleet of standardized vehicles, generally called the M-series, retaining the 1/4-ton jeep in the incarnation of the M38 and M38A1, the 3/4-ton truck as the M37, and the 2-1/2-ton truck as the M35 and M211, but dropping 4- and 7-ton trucks in favor of 5- and 10-ton vehicles. It’s a mystery, though, why 1-1/2-ton trucks were phased out, because this left a significant transport gap between the 3/4-ton and 2-1/2-ton vehicles.
The 1-1/2-ton trucks, most notably the Chevrolet G-506, had certainly proved their usefulness during WWII, but perhaps it was thought that the 3/4-ton M37 pulling its 3/4 ton M101 trailer could bridge that gap. This concept works on paper, but not always in practice, because cargo loads can’t always be split 50/50.
The military did attempt to fill this gap a little more effectively in the late 1960s with the M715 1-1/4-ton truck and the 1-1/2-ton M561 Gama Goat, but both vehicles were problematic. During the 1970s, various CUCVs (Commercial Utility and Cargo Vehicles), such as the Doge M880, in the 1-1/4 ton range were utilized, while the role of 1/4-ton truck was performed by the M151 MUTT.
A MULTI-PURPOSE VEHICLE
In the late 1970s, the military drew up specifications for a high mobility multipurpose wheeled vehicle (HMMWV) to replace all tactical vehicles in the 1/4- to 1-1/4-ton range—the M151, M715, and M561, as well as many CUCVs—with one vehicle. The requirements included high ground clearance, low silhouette, superior mobility, and speed, both on highway as well as in tactical field operations. Several companies submitted initial proposals. Only three, General Dynamics, Teledyne, and AM General—the latter already building M151 MUTTs and M35 2-1/2 ton trucks—were interested enough to actually submit prototype vehicles.
Teledyne’s prototype was based on an existing vehicle, the Cheetah. AM General started from scratch and delivered its prototypes for testing in April 1982. The vehicles proved satisfactory, and AM General was awarded a contract for development of several more prototypes.
The original M998 HMMWVs had an unladen weight of 5,200 pounds with a payload of 2,250 pounds. Each was fitted with a 6.2 liter V-8 General Motors diesel engine and a three-speed GM automatic transmission.
After rigorous testing, AM General was awarded a production contract in 1983. It called for 55,000 vehicles to be delivered within a five-year period.
THE AM GENERAL HMMWV
The first HMMWVs were configured as six basic types: Cargo-Troop Carrier, Armament Carrier, TOW Missile Carrier, Ambulance Carrier, Shelter Carrier, and Prime Mover. Based on these first types, more than twenty variants were developed, many of which differed from one another in only minor ways. For example, there were seven different variants of Cargo/Troop Carrier and eight different variants of Armament Carrier.
Since HMMWV production began, many new variants have been developed, while others have been discontinued. The HMMWV was, indeed, able to effectively replace some vehicles in the U.S. military’s tactical fleet, such as the Dodge M880 and other CUCVs, and the M561 Gama Goat. But due to its size , the HMMWV proved less effective trying to play the role of the much smaller M151 MUTT, a problem that was always apparent but which became glaringly obvious in Afghanistan where the HMMWV was too large to traverse some mountain roads and village streets.
As noted, the first HMMWVs were fitted with a 6.2-liter G.M. V-8 diesel engine—the same used in many GMC Suburbans—with a rated net horsepower of 150 and a gross horsepower rating of 165 at 3600 rpm. Current models use the GM 6.5 liter engine, which produces 160 net horsepower at 3400 rpm. A 25 gallon fuel tank provides an operating range of around 250 miles.
The HMMWV’s body tub, rear fenders, and tailgate are made from heat-treated aircraft-quality aluminum, with the panels bonded and then riveted together. The hood is hinged at the front to swing up and away from the windshield, and is made from a composite of fiberglass and plastic.
The HMMWV’s off-road capabilities are enhanced by 16 inches of ground clearance with outboard-mounted geared axle hubs, full-time four-wheel-drive and independent suspension, plus steep approach and departure angles. HMMWVs have a 60 percent slope climbing ability, and can operate on 40 percent side hills. They possess a normal 2.5 foot water-fording capability which is increasable to 60 inches when equipped with a fording kit, though despite a few myths are not amphibious. HMMWVs may also be fitted with a Central Tire Inflation System (CTIS) which, as on the WWII DUKW, allows the driver to inflate or deflate the tires from inside the cab for better flotation or traction depending upon the terrain.
HMMWVs had an advantage over other vehicles in the U.S, Military’s tactical fleet, that of being a multipurpose platform... though to a lesser degree the same could be said for vehicles such as the M37 and M35. Beginning with the first six types, many improvements were made, and the basic model was upgraded to the M998A1 and then M998A2.
HMMWVs were soon available in fifteen different configurations, yet all shared the same engine, chassis and transmission, along with many other interchangeable parts. This meant fewer training hours for motor-pool mechanics, as well as simplified supply and maintenance. In other words, a HMMWV was basically one set of major components for many different vehicles.
Current model HMMWVs, M998A2 or M1097A2, were initially called “Heavy Humvees” because they weigh about 700 pounds more than earlier units. Full specs are as follows:
Engine: GM V8, 6.5L Diesel. Naturally Aspirated
Horsepower (@3,400 RPM): 160
Torque (@1,700 RPM): 290 lb.-ft.
Governor Type: Mechanical
Displacement: 400 cu. in. (6.5L)
Bore & Stroke: 4.06x3.82 in. (10.3x9.7 cm.)
Compression Ratio: 21.3:1
Fuel Capacity: 25 gal. (94 L)
Transmission: 4-speed automatic with a maximum input torque rating of 451 lb. ft.
Gear ratios: 1st - 2.48:1, 2nd - 1.48:1, 3rd - 1.0:1, 4th - 0.75:1, Reverse - 2.08:1
Torque converter ratio: 21:1
Transfer Case gear ratio: Low - 2.72:1; High - 1.01:1
Axles: Hypoid with a ratio of 2.73:1
Geared Hubs: ratio: 1.92:1
Frame: Steel box section with five cross members.
Electrical: 24 volt waterproof. 100 amp. and 200 amp (200 amp. alternator standard on the M997A2.)
Steering: Power assisted with a variable ratio of 13/16:1
Differential: Torque Biasing Differential
Brakes: Hydraulically actuated, four wheel inboard mounted power disc brakes with dual reservoir master cylinder. Parking brake manually activates the rear service brakes.
Suspension: Independent double A-frame with open end coil springs and hydraulic shock absorbers.
Tires: 37x12.5 R16.5 LT load range “D” Radial with beadlock and runflat device
Wheels: 3,400 lbs. (1,542 kg.) capacity, 16.5x8.25 2-piece take-apart
As reported, a HMMWV can accelerate from 0-30 (yes, 30!) mph in about eight seconds. Fuel consumption is approximately 10-11 miles-per-gallon at 55-60 mph The safe top speed is about 70 mph, though the engine is usually governed to keep the speed around 60, and in some cases 55 mph.
The first production M998s were equipped with a 3-speed GM automatic transmission, while newer units have a GM 4-speed. All HMMWVs have automatics. The vehicle was designed to be simple to operate, and an automatic transmission gives the driver one less thing to think about under combat conditions. It also makes it easier for a wounded soldier to drive the vehicle, as well as minimizing training time for young GI’s who never learned how to drive a stick.
Though having full-time, four-wheel-drive, a HMMWV spends most of the time with its center differential unlocked. This permits the axle differentials to divide the torque and keep the tires from spinning in slippery situations. Even on more extreme terrain, the center differential may still be left unlocked. When the going really gets rough, the driver can then lock the center differential...though HMMWVs have some problems climbing steep slopes in loose dirt or sand. All major power-train components are mounted above the frame and protected by skid plates. HMMWVs may be fitted with a Warn Mil-12000 winch.
There are over twenty variants of HMMWVs presently in service with the U.S. Military, including cargo/troop carriers, automatic weapons platforms, ambulances (four litter patients or eight ambulatory patients), M220 TOW missile carriers, M119 howitzer prime movers, M1097 Avenger Pedestal Mounted Stinger platforms, MRQ-12 direct air support vehicles, S250 shelter carriers, and other roles. Primary models include:
M56 Coyote Smoke Generator Carrier
M966 TOW missile, Armored
M996 Mini-Ambulance, Armored
M997 Maxi-Ambulance, Armored
M998 Cargo/Troop Carrier
M1025 Armament Carrier, Armored
M1026 Armament Carrier, Armored, with winch
M1035 Soft-Top Ambulance
M1036 TOW Missile, Armored with winch
M1037 Shelter Carrier
M1038 Cargo/Troop Carrier with winch
M1042 Shelter Carrier with winch
M1043 Armament Carrier, Up-Armored
M1044 Armament Carrier, Up-Armored with winch
M1045 TOW Missile Up-Armored
M1046 TOW Missile Up-Armored Armor with winch
M1069 Tractor for M119 105-mm Gun
M1097 Heavy Avenger
M1109 Up-Armored Armament Carrier
Three HMMWVs can be carried in a C-130 Hercules, six in a C-141B Star-Lifter, and fifteen in a C-5A Galaxy. Two HMMWVs can be slung from a CH-47 Chinook or a CH-53 helicopter, while one may be slung from a UH-60A Blackhawk. HMMWVs can be also be delivered by Low Altitude Parachute Extraction without the aircraft having to land.
HMMWVs may be fitted with a wide range of weaponry, including 7.62 mm and .50 caliber machine guns, the MK 19 40 mm grenade launcher, or a TOW missile system.
Armor kits include the Armor Survivability Kit (ASK), and the FRAG 5 and FRAG 6. The ASK adds about 1,000 pounds to the weight of the vehicle. The Marine Armor Kit (MAK) offers more protection but increases the weight even more. The FRAG 6 kit not only adds more than 1,000 pounds but also increases the HMMWVs width by 2 feet. The heavy doors require a mechanical assist to be opened and closed. Additionally, during an accident or attack, the armored doors may jam shut, trapping the occupants inside. The doors of some Up-Armored HMMWVs are fitted with outside hooks so they can be pulled off by another vehicle. Vehicle Emergency Escape (VEE) windows were also developed.
PRIVATE OWNERSHIP OF SURPLUS HMMWVs
As should be apparent, and like most vehicles, HMMWVs have their share of limitations, problems and quirks. As mentioned, one problem is simply the size, which can make it difficult or impossible to drive off-road where smaller vehicles can go with ease. Someone considering a purchase may want to pace off an approximate space of 15 by 7.5 feet in their shop, garage or driveway... add another two feet to the width if pondering an Up-Armored variant.
Speaking from experience, driving a HMMWV is rather like cruising around in a 1-1/2-ton dually pickup with the entire vehicle being the width of the duals (add two more feet if Up-Armored) while being locked in the engine compartment of a Greyhound bus. Nor, as when driving a large vehicle such as an M35 or even a G-506, do you sit high above most other traffic for good visibility. Of course, tastes and tolerances vary!
Being much more high-tech than most common collectible HMVs, a HMMWV’s mechanical or electrical problems can be difficult to diagnose and repair in a home workshop or out in the field. Replacement parts are not cheap, though parts availably continues to increase. Like MUTT parts, HMMWV parts will probably be available for many decades into the future.
As with most newer vehicles, a HMMWV has relatively few lubrication points compared to HMVs such as the M37 or M35: instead it uses replaceable bushings and fittings in its suspension and steering system. The key word is “replaceable.” This is not a vehicle that one simply greases at regular intervals and its chassis lasts indefinitely. Components such as control arm ball joints, suspension bushings and steering linkage wear out fast in a unit that is driven daily, and much more so if the vehicle is used off-road. As with any vehicle, worn out suspension bushings will affect wheel alignment, causing irregular wear on the tires.
If you are considering a HMMWV, stay tuned. Part Two of this series will cover what to look for when shopping.
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