The Willys MB or Ford GPW army jeep is the one most people think of when talking about military jeeps. It is known by many names, such as the Willys Jeep, the GI Jeep, the World War II jeep, or just plain Army jeep. This jeep resulted from a 1940 design competition that involved American Bantam, Willys-Overland, and Ford. Willys was chosen for the first mass production contract based on the Willys MA design, but the Willys MB which followed incorporated superior features from the Bantam BRC-40 and the Ford GP in addition the the Willys MA. When the War Department realized that hundreds of thousands of jeeps would be needed for World War II requirements, Ford was given a contract to produce the Willys MB design. Ford produced jeeps were designated GPW.
Early Willys MB with slat grill, Australia, 1942.
The Willys MB or Ford GPW jeep of World War II were externally visually the same but with many small differences in production details. It was also common to install parts from Willys into a Ford jeep and vice versa. As WW II went on, field maintenance facilities used whatever parts were at hand without regard to the original manufacturer of the part or the jeep.
To discover the origin of a particular jeep, the original dataplate is the best source. Unfortunately, the data plate is often missing or has been replaced by an unreliable replica. The engine has a stamped serial number, starting with MB or GPW which will tell you the origin of the engine. But, like all other parts, the engine may not be original. There are many other details of the Willys MB or Ford GPW that are different. If you are with the jeep, you can see if it has the Ford script F embossed on the rear panel of the body tub or has the F stamped on most bolt heads.
The early production Willys MB jeeps, about 25,800 of them, had a grill made of vertical welded slats (called the "slat grill" type, photo right) and had "Willys" embossed in the back panel among other small differences. When Ford began producing the nearly identical GPW (with Ford embossed on the back panel) in January of 1942, they used the now-standard, less expensive stamped steel slotted jeep grill (photo above, left). The Army wanted full parts interchangability and worked with Ford and Willys to get one standard design for both jeeps -- the Ford idea for the grill was better, so Willys changed over to the stamped grill by April 1942. The Army also insisted that both Willys and Ford drop the embossed company name from the jeep exterior.
The main chassis or body component that distinguished a Willys-Overland MB from the Ford-built GPW is the tubular front frame cross-member on the MB as opposed to the inverted U-shaped cross-member on the GPW with a flat top. That cross-member is located behind the grill, at the base of the radiator so it usually cannot be seen in photos. Below are two close-up photos showing the difference.
1943 Willys MB, with rounded, tubular front cross-member.
1942 Ford GPW, with flat top, rectangular front cross-member.
A visible sign is that GPWs with Ford frames, unlike MBs or GPWs with Willys frames, had holes in the front bumper in line with the frame rails and also had holes in the rear cross-member just out from the bumperettes (photo, above left). Another small MB/GPW difference is in the lid of the rear fender tool boxes. The often replaced, factory original MB tool box lid is flat while the GPW has an embossed ridge and circle design. [Thanks to Tom Wolboldt for help with GPW ID.]
At the outset, all engines were produced by Willys but in 1942 Ford began to produce GPW engines to the Willys design. Midland Steel Corp. produced frames to the Willys specification and wre used by both Willys and Ford. Ford contracted with Murray Corp. for frames for the GPW after which Ford no longer used the Midland frames. During 1941 to 1943 Willys and Ford manufactured their own bodies, slightly different from each other. In January 1944, both Willys and Ford subcontracted their jeep bodies to American Central Body of Connersville, IN, who built the so-called "composite body" used by both manufacturers.
Willys MB with slat grill, reference photo from TM 10-1207 published in 1941.
After about 25,000 units were produced, in early 1942 the MB/GPW was standardized with changes agreed upon by Ford, Willys and the Army. The 1941 and early 1942 production jeeps have many small differences from the later, full production models. The most visible change was the Ford nine-slot stamped grill which replaced the Willys slat grill (similar to the Ford GP) in March-April 1942.
1942 jeep assembly line at Ford. Photo: Courtesy Ford.
1945 jeep assembly line at Ford. Photo: Courtesy Ford.
Ford's River Rouge plant produced the first 77 GPWs with Willys engines and Midland frames in January 1942. Willys jeeps were produced in their Toledo, OH plant, while Ford had assembly operations at six plants around the country. Although small differences remained, the MB and GPW essentially met the Army's goal of being completely interchangeable in all parts. At the factories, there were Ford GPWs produced on Willys Midland frames or with Willys engines, plus other production expedients and subcontractor sharing, creating a mix of jeeps and parts to be sorted out by later generations.
During the course of the war, Ford built 277,896 GPW jeeps, and Willys built 335,531 units. Production contracts were terminated in the summer of 1945 as World War II ended. The last Ford GPW was built on 30 July 1945 and the last Willys MB rolled off the Toledo assembly line on 20 August 1945.
Specifications of the Willys MB / Ford GPW Military Jeep
Height, top up
Height, top down
Willys or Ford 4 cyl L-head, 134.2 ci, 6.48:1 compression
54 @ 4,000 rpm
Warner T-84J 3 speed synchromesh
Dana Spicer 18 2 speed
Spicer Dana 4.88:1 23-2 rear, Dana 25 front
6v, neg ground
Weight w/o gas and water
21 inches max
Tabulated data from TM 9-803, February 1944. All Willys MB and Ford GPW jeeps have a serial number tag on the left front of the frame. The serial number appears in other locations and there is also a non-matching engine number.
Manuals the Willys MB / Ford GPW
The WW II jeep (Willys MB / Ford GPW) was originally under the authority of the Quartermaster Corps. Therefore, the original manuals were 10-series QM manuals, later superseded by 9-series Ordnance manuals. The QM manuals included:
TM 10-1186 Parts Willys MB
TM 10-1206 Parts Willys MB
TM 10-1207 Parts Willys MB
TM 10-1348 Parts Ford GPW
TM 10-1349 Operation & Maint Ford GPW
TM 10-1512 Parts Willys MB
TM 10-1513 Operation & Maint Willys MB
The Ordnance manuals included:
TM 9-803 Operation & Maint MB/GPW
TM 9-1803A Engine & Accessories MB/GPW
TM 9-1803B Power Train, Body & Frame MB/GPW
LO 9-803 Lubrication Chart
SNL G-503 Standard Nomenclature List of Spare Parts and Equipment
ORD 7 SNL G-503 Organizational Spare Parts & Equipment
ORD 8 SNL G-503 Higher Echelon Spare Parts & Equipment
ORD 9 SNL G-503 List of all Service Parts
The lists are not exhaustive. For example, there are many specialized manuals such as TB 9-1830A-2 "Fits, Tolerances, and Wear Limits for Willys-Overland MB Engine" as well as separately printed changes, MWOs (eg, MWO ORD G503-W7), and more. Manuals exist for boxing partially assembled Willys MB and Ford GPW jeeps paired with manuals for unboxing and assembly. Other related manuals cover specific parts (eg, the Carter carb or speedometers), or general automotive procedures and tools. Multiple versions of these manuals appeared with different dates, starting in August 1941.
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