Military HMMWV

Apr. 01, 2002 By Gerald Luiz
This section gives background information about the creation of the HMMWV. the basis of the civilian HUMMER. As always, questions, comments, and corrections should be sent to the author by using the Feedback button.



In the late 70's, the US Army realized that it had too many vehicles doing different jobs that a single vehicle family should be able to do. Some were created for a particular job and were questionably successful at doing the job. The military wanted a single, more versatile family that could be tailored to specific duties while remaining virtually mechanically identical.

In 1979, the military announced a competition for the design of a new vehicle and released preliminary specifications. At the beginning of 1981, the Army released the final specifications for the new vehicle called the High Mobility Multipurpose Wheeled Vehicle, HMMWV. The specifications would allow the HMMWV to replace several vehicles in the current inventory while providing capabilities beyond any other vehicle.

The specs gave requirements for both the shape and mechanics of the vehicle. Roof height, hood height, and profile were defined. Furthermore, the military wanted to standardize mobility for combat vehicles so that all could remain together. Therefore, the HMMWV had to meet the same specs as the Bradley's and M1 tanks. The 16" ground clearance, 60% grade, 40% side slope, 18" vertical step, 30" fording w/o preparation, etc. are the military's mobility requirements for combat vehicles, including the HMMWV.

Starting in 1979, AM General, Chrysler Defense, and Teledyne were interested in the contract. AM General did not have anything in production that would meet the (still forthcoming) specifications and started a totally new design. The Chrysler vehicle was based on the Saluki. The Teledyne was based on the Cheetah. [Trivia - the Cheetah is the Lamborghini LM design (e.g. LM002). When Lamborghini and Teledyne lost the contract, Lambo turned the Cheetah into the LM series of luxury desert cruisers.]

Prototype vehicles were delivered to the military for initial evaluation. Problems were noted and the designers had to submit design/part changes and test the new assemblies. If Army liked the changes, preproduction models were requested and entered into durability and performance testing (Phase I) at test facilities. Phase II testing was done by actual soldiers in the field. Phase III tested the vehicle in different terrains (desert, grasslands, etc) and for the marine environment (Marine Corps). After all vehicles had passed the tests, a contract would be issued.

AM General was the first to complete the testing. Since the vehicle was also the lightest and best performing, AM General won the contract and the HMMWV as we know it was born.

The HMMWV replaced the M151 1/4 ton Jeep, M274 1/2 ton Mechanical Mule, M561 1 1/4 ton Gamma Goat, M718A1 Ambulance, M792 Ambulance, and some M880 1 1/4 ton trucks.

On March 22, 1983, the Army ordered 55,000 HMMWVs for $1.2 billion. They were to be delivered over a 5 year period with 15 different configurations. The Army increased the orders to 70,000 vehicles. In 1989, AM General received another 5 year contract for 33,000 more.

The Original 15

The advantage of the HMMWV is that it can be used in a variety of roles while still remaining mechanically identical. The military refers to all HMMWVs (pronounced Hum-Vee) generically as M998, M998A1, or M998A2. Different models actually have different designations but share the same frame, suspension, drivetrain, hood, and lower body.

Originally there were 5 models: Cargo/Troop Carrier, TOW Carrier, Armament Carrier, Shelter Carrier, and Ambulance. From these, 15 configurations were produced. All configurations (except M1037/M1042 Shelter Carriers) have a payload of 2,500 lbs (1 1/4 or 5/4 ton) with varying GVWs.

    m998 drawingM998 - Cargo/Troop Carrier
    M1038 - Cargo/Troop Carrier with winch
    (Ignore the dotted line in the picture)
    The most common version of the HMMWV. These types can be changed in the field easily for different roles. When used as a Cargo Carrier, the M998/M1038 looks like a 2 door pickup but has a soft top roof over the 2 passenger cab. The rear can be open or covered with a low or high profile soft cover. In the troop version, bench seats over the rear fenders allow seating for 8 which can be covered. Alternatively, 4 doors can be installed with 2 conventional seats in the rear (4 seats total) and a small pickup bed in the rear. A weapons mount can be installed and can use the same weapons as the M1025/M1026 below, however, the US does not use any such configuration. The passenger and cargo compartments can be covered. The doors (if installed) are just canvas over a metal frame. No armoring. 2,500 lbs payload, GVW of 7,700 lbs.

    m1025 drawingM966 - TOW Carrier, armored
    M1036 - TOW Carrier with winch, armored
    (Pictured is a M1025 with an M60 - imagine the TOW from the M1045 picture)
    These have 4 hard doors and a metal roof. The rear can be covered by a composite slant or square back to store 6 extra missiles. The doors are made of a fiberglass reinforced with a Kevlar-like composite with operable polycarbonate windows. The hood vents have baffles to prevent spall from damaging the engine. The windshield is bullet resistant. The tires use the runflat system. Contrary to popular belief, TOW carriers are only spall resistant and cannot withstand direct small arms fire. The roof has a hatch with a rotating circular weapons ring and a TOW mount providing a 360 degree field of fire. TOW stands for Tube launched, Optically sighted, Wire guided. The operator uses the optical sight for targeting. The missile is launched from a tube, spooling out wires as it flies. The wires allow the operator to steer the missile in flight. Hence, as long as the operator tracks a target, the missile will follow. The TOW missile's shaped charge warhead is able to defeat all armor. The TOW gives infantry higher lethality against armor than the personal LAW with great mobility. The TOW launcher can be dismounted from the vehicle. M966/M1036s can also be deployed as AT teams. GVW of 8,200 lbs.

    M1045 - TOW Carrier with supplemental armor
    M1046 - TOW Carrier with winch and supplemental armor
    A M966/M1036 with additional armoring. Steel plates are placed over some panels to improve fragmentation (spall) resistance. However, direct fire bullet-resistance is not significantly improved. I believe that the Marine Corps is the only ones to use this variant. GVW of 8,400 lbs.

    m1025 drawingM1025 - Armament Carrier, armored
    M1026 - Armament Carrier with winch, armored
    Nearly identical to the M966/M1036 TOW Carrier but with a pintle mount on the weapons ring. The weapons ring can accommodate the 40mm MK19 Mod 3 grenade launcher, M2HB 50 caliber machine gun, M60 7.62mm machine gun, and the M240 7.62mm machine gun. The Armament Carriers have the same protection as the basic armored M966/M1036 TOW Carriers. GVW of 8,200 lbs.

    m1043 drawingM1043 - Armament Carrier with supplemental armor
    M1044 - Armament Carrier with winch and supplemental armor
    The M1043/M1044 are M1025/M1026 Armament Carriers with additional armoring like the M1045/M1046 with equivalent protection. Marine Corps only variant. GVW of 8,400 lbs.

    m1037 drawingM1037 - S250 Shelter Carrier
    M1042 - S250 Shelter Carrier with winch
    (Remove the stake side and imagine the dotted line as a solid box in the picture)
    Basically a M998/M1038 Cargo Carrier with changes to the electrical system and cargo bed. Shelters are large boxes placed in the bed and tall enough to almost stand in. Different shelters perform different functions like CP or radio units. Different shelters can be loaded on to meet the mission requirements. 3,600 lbs payload with a GVW of 8,660 lbs.

    M996 - Ambulance, 2 litter, armored
    The M996 Mini-Ambulance has two hard doors and a rear wagon like body with a slightly elevated top. It can carry 2 litter and 3 ambulatory patients and a driver. It has the basic armor like the M1025/M1026 Armament Carriers. GVW of 8,660 lbs.

    m997 drawingM997 - Ambulance, 4 litter, armored
    The M997 Maxi-Ambulance also has two doors but with a longer and taller rear section. It can provide comprehensive care to 4 litter patients or can carry 8 ambulatory patients and the crew of 2. It also has its own AC, heating, and power generation. It has the basic armor like the M1025/M1026 Armament Carriers. GVW of 9,100 lbs.

    m1035 drawingM1035 - Ambulance, 2 litter, soft top
    The M1035 can carry 2 litter and 3 ambulatory patients patients with the driver. It is a soft top with a low soft top enclosure. It has no armoring. GVW of 7,700 lbs.

Major Revisions and Configuration Changes

The original HMMWV uses the Detroit Diesel 6.2L V8, 150hp, 250 lbs-ft, TH 400 3sp automatic, NPG 218 full-time 4wd transfer case with a 2.61:1 low, AMC 20 housings with 2.56:1 differential gear ratios, Torsen differentials, 1.92:1 geared hubs, 4 wheel independent suspension, 2 piece wheels with bias ply Goodyear Wrangler RT/II tires, and 25 gallon fuel tanks. The hood is a fiberglass composite and the body is made of 6061T6 aluminum. All configurations (except M1037/M1042 Shelter Carriers) have a payload of 2,500 lbs (1 1/4 or 5/4 ton) with varying GVWs. The basic M998 has a curb weight of 5,200 lbs.

When the 105mm M119 Light Howitzer entered service, the M1069 Prime Mover HMMWV was introduced. The M119 and M1069 Prime Mover and more easily air transportable than the older 105mm howitzer and can also use newer ammunition.

Eventually the military wanted a higher payload capacity and in 1991, AM General began investigations. The result was the M1097 Heavy HMMWV Variant (HHV). It has a payload of 4,400 lbs and curb weight of 5,600 lbs for a GVW of 10,000 lbs. and a higher towing capacity. It entered production in late 1992. Rear springs, spring seats, frame crossmembers, and shocks were modified (but not the engine or drivetrain). The M1097 was basically designed as new type of Shelter Carrier, however, it can also be a Cargo/Troop Carrier. AM General also released a kit to upgrade all of the other models with the new components to increase standardization and durability.

Seeing a new application for the HMMWV using the HHV chassis, AM General developed a superior armor protection system for the weapons carriers, the Up-Armored HMMWV. Ballistic materials are added to both the interior and exterior. The windows are 1.6 inch thick, non-spalling polycarbonate. The weapons station optionally gets armor also. The result is 360 degree occupant protection from 7.62 mm AP rounds. The roof can withstand 155mm airburst fragments. I also believe it protects against direct 7.62mm ball but not AP rounds (oblique only). Optional underbody panels protect against 4 lbs antipersonnel or 12 lbs antitank mines. The engine and rear cargo compartment do not get any additional protection beyond the basic armor kit. The military has very few of these up-armored units (<75 ordered in 1992), designated XM1109, b/c of the loss in cargo capacity.

In early 94, the A1 series came out. The A1s had all the M1097 chassis upgrades, some interior changes, new rear halfshafts, and some electrical changes. Once again, the engine was untouched. I believe that the transfer case was replaced with the NPG 242 full-time transfer case with a 2.72:1 low range, the differentials were changed to a 2.73:1 ratio, and the new 2 piece wheels with the radial Goodyear 37x12.50/16.5 MT were used.

Almost all models continued in the new A1 configuration (e.g. M998A1, M1025A1, M1097A1, etc). The GVWs were increased by 180 lbs (except the M1097A1 was still 10,000 lbs). The M1097A1 replaced the production of the M1037/M1042 as the Shelter Carrier.

In 1995, the A2 series was introduced. The A2s are based on the A1s but use the Detroit Diesel 6.5L V8 diesel (170 hp, 290 lbs-ft) and the 4L80E electronically controlled 4 sp automatic. They are also Central Tire Inflation System (CTIS) ready, i.e. CTIS is field installable with a kit. Some further changes to the interior, heater, and cargo mounts. I also believe that they switched to the larger halfshafts. All A2 models have a GVW of 10,300 lbs with available payload depending on the curb weight. Note that the M1097A2 payload did not increase. My theory is that the M1097A1 caused a loss in mobility b/c of the higher weight. The 60% grade figure is actually a power rating. The 6.2L and 10,000 lbs payload, even with the new gearing, could not achieve the 60% grade rating. The switch to the 6.5L allows it to meet performance figures.

With the A2 release, some of the model numbers were simplified. There is no longer a different number for vehicles with or without winches. It is now considered an option that can be installed or removed as the mission requires. For example, the M1025 and M1026 turned into the M1025A1 and M1026A1, and then into the M1025A2. The M1097A2 is actually classified as a Cargo/Troop/Shelter Carrier and replaces the M998A1 and M1038A1 Cargo/Troop Carrier in production. The M1097A1 had replaced the M1037/M1042 Shelter Carriers already. With the additional payload, the M1097A2 can be fitted with a TOW launcher, 30mm ASP-30 auto cannon, or a 50 caliber GAU-19/A 3 barrel Gattling gun. Like in the M998 case, the US military M1097A2s do not use the weapons mount. Note that the latest HMMWV models are still generically referred to as M998A2 even though there is no such number anymore.

As another simplification, the Army no longer differentiates between the TOW and Armament Carriers b/c they can carry either. The M1025A1/M1026A1 Armament Carrier became the M1025A2. The M996A1/M1036A1 TOW Carrier became the M1025A2 TOW/Armament Carrier also. To further confuse matters, the US Marines decided to keep the models separate. They have a M1043A2 Armament Carrier and a M1045A2 TOW carrier, both with supplemental armor.

The M1097A2 also becomes the basis for the new Expanded Capability Vehicle (ECV). The ECV ups the payload from 4,400 to 5,300 lbs, curb weight from 5,900 to 6,200 lbs for a 11,500 lbs GVW. The ECV uses modified differentials, brakes, halfshafts, wheels (1 piece), runflats, and frame. Many of these components come from the Cab-Over HMMWV Variant (COHV). The ECV also uses the Detroit Diesel 6.5L V8 turbo diesel (190 hp, 385 lbs-ft) to maintain the performance figures. The ECV comes from the factory with CTIS and AC installed. The body from the Up-Armored HMMWV, the XM1109, is placed onto this frame and is called the M1113 Up-Armored ECV. It comes in a square or slant back that is armored or unarmored. Furthermore, the hood can be armored also. It uses the additional underbody panels for occupant mine protection (4 lbs AP, 12 lbs AT). It offers full 360 degree occupant protection from 7.62mm AP rounds. The M1113 offers the protection of the XM1109 with no loss in payload. The US Army uses two versions of the M1113: the M1114 Armament Carrier and the M1115 TOW Carrier.

Other Variants

There are a few additional variants of the HMMWV that I know of and am sure there are quite a few more.

    The original Avenger was mounted on a M1037 Shelter Carrier. The Avenger system is a rotating turret on the back of the HMMWV with 8 Stinger anti-aircraft missiles along with a 50 caliber machine gun. It has all the necessary equipment to track, identify, and engage aircraft. The turret can be controlled from within or remotely. Note that the Stinger is the current AA missile for infantry b/c it can be fired from a shoulder launcher.

    Civilian HUMMER
    Sometimes people call the military HMMWVs as HUMMERs or vice versa. Technically this is wrong. The military HMMWVs are called "Hum-Vees". The commercial (a.k.a. civilian) models are called HUMMERs. While they are closely related, there are differences between the families.


  • HMMWVs are bullet proof
    If you have read the above, you know that unarmored versions like the M998 have almost no protection from spall or direct fire beyond what naturally occurs from the aluminum and glass. Even the armored versions like the M1025 or supplementally armored version like the M1043 are only spall resistant. It was not until the XM1109 and M1113 that true bullet proof versions existed.
  • The HUMMER's CTIS (Central Tire Inflation System) came from the military HMMWV
    Prior to 1995, no military HMMWV had CTIS. The A2 models are the first to be CTIS-able from the factory. The M1113 series are the first to have CTIS from the factory. CTIS existed in civilian versions since 1992. It just happened that the geared hub design allowed for easy integration of the system.
  • Similar to CTIS, the 6.5L diesel engine was first available in commercial versions before the military. However, the 6.5L TD were introduced in the ECV and 96 HUMMER at about the same time.
  • The new rims on the ECV were required b/c of the higher payload. These are also the rims in use on the late model 1996 civilian versions. I believe that AMG now uses the rims on all HUMMERs and HMMWVs.
  • The windshield folds down
    On models like the M998 and M1037, the windshield can be folded down. For most other models this is not possible. The folding is not a quick process, it is only used to reduce the height to reduce the shipping cube. Many military vehicles remove the front windshield glass to reduce reflection.
  • The winch is made by Warn
    Yes. The original winch was a Mil-6000 (6000 lbs first layer) and later a Mil-9000. Both are 24VDC electric with 100 ft of 3/8" EIPS cable. They will work underwater (see below). They are different from the standard Warn winches.
  • HMMWVs don't float. They can go through 30" of water at any time. If the deep-water fording kit is added, they can go through 60" of water (mid-windshield). The kit snorkels the intake and exhaust and changes some of the venting system.
  • What are these 60% grade, 40% side slope numbers?
    The side slope grade percentage gives an idea of the stability of the vehicle on good traction surfaces at GVW. The 60% grade figure is actually a power rating. 60% on a good traction surface is pretty easy, however at 10,300 lbs, it requires good power and gearing.
  • You can buy a military HMMWV
    HMMWV are not DOT approved so you have to get a civilian version. Officially, HMMWVs are de-militarized before being surplused. This means that the frames are cut, bodies crushed, etc. So in general, you cannot buy a surplus one either. There are some put together HMMWVs out there and some stolen ones. Be careful with your money.

HMMWV Photo Gallery

The HMMWV Photo Gallery contains pictures of various configurations. Note that some images are large. Newsletter
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