Army test drivers were told to drive the test Jeeps until something broke, then report the problem to Willys, which would then engineer a stronger replacement part. The result was a light but extremely strong vehicle that could be produced for a relatively low price.
72 The Spicer 25 front axle used on the wartime Willys Jeep MB is a full-floating design combining the stability of a hypoid design with steerable front knuckles at the outer ends of a rigid axle housing. This combination provides good maneuverability and outstanding durability in off-road situations.
73 As sturdy as the Willys Jeep was, during early prewar days the test drivers at Camp Holabird were tougher, running the test vehicles around the clock with specific instructions to keep pounding them until something broke. One test Jeep suffered a cracked frame at 5,184 miles; another had its engine cylinders so badly worn out by 5,011 miles that the engine had to be replaced. The army had no spare engines on hand, so a couple of enterprising mechanics from Willys-Overland pulled the engine from a civilian Willys car in the parking lot!
Other problems that showed up in early testing included transfer case main bearing failures, steering pin failures, and several spring and suspension failures. The army testers forwarded their report to the Quartermaster General, who told Willys it better fix the problems if it wanted to keep the contract. Barney Roos, Willys vice president of engineering, conferred with suppliers and with Willys’ own manufacturing people and ordered them to beef up the weak parts ASAP.
74 A report found in the files of Willys-Overland refers to a wartime effort to produce a Jeep without a carburetor. Exactly how that would have worked isn’t mentioned, and I wonder if the test reports on that effort are stowed away in some obscure file at Jeep.
75 In addition to all of the Jeep vehicles it produced for World War II, Willys also produced 83,000 Go-Devil engines that were mounted and used as stationary power units and electrical generators. The company also produced the Robomb (rocket-bomb), which was the US Army’s answer to the German V-1 and V-2 rockets.
The military chose the Willys Jeep MB to be the standard Jeep for the armed forces and contracted with Ford to produce them. The Ford units are dubbed GP-W (for General Purpose) Willys. The MBs and GP-Ws are nearly identical and were designed for easy shipping.
76 By 1952, the Go-Devil was once again out of date and in need of replacing. The new Jeep M38 (Willys MC) weighed about 2,750 pounds and fully loaded could weigh just under 2 tons, which is a very heavy load for 60 hp to pull. So, when the M-38A1 was being developed, increased horsepower was ordered.
Willys management was still extremely frugal with capital investments and didn’t want to shell out the money for an all-new engine, so it instructed its engineers to somehow squeeze more juice out of the aging Go-Devil. Willys’ chief engineer Barney Roos and engineer A. C. Sampietro (Floyd Kishline had left the company) went to work on the little mill. Sampietro designed a new F-type cylinder head for the Willys mill that boosted output to 72 hp, another 20-percent boost.
77 Okay, so you’re asking: What exactly is an F-head? It’s an engine with one valve in the block, similar to an old-style L-head (or flathead) engine, and one valve in the head, similar to an OHV engine. It provides much better breathing compared to a flathead engine and thus more power. It’s a relatively cheap way to boost power in an old-style engine.
78 The little Willys Whippet 4-cylinder engine, introduced for 1926, remained in production through at least 1971 for the United States, and even longer in export markets. It became the Go-Devil engine in 1938 after Willys’ engineers went through it with a fine-tooth comb, ironing out all its bugs. Then it received another large power boost with the introduction of the F-head Hurricane version in the 1950s.
It was offered in nearly all of the postwar Willys vehicles. After Kaiser Motors took over the company, it was kept in production as the standard engine on all Kaiser Jeep CJ Jeeps, and even for the DJ-5 and DJ-6 models, as well as the Jeepster Commando series, despite it being sorely out of date by then. I asked a retired Kaiser Jeep vice president why the company continued to produce the hoary old Hurricane for so long when it was out of date, and he replied, “We did it simply because it was very cheap to make.” Oh.
This experimental multifuel engine was designed and built by Willys Motors’ engineers for the military. The goal of using multifuel engines was to make it easier to obtain and use different fuels in forward areas where gasoline might not be available, but diesel or kerosene was.
79 The 1950–1951 military M38 Jeep (also known as the Willys MC) still had the classic flat fenders up front but was given a stronger Spicer 44 rear axle and sturdy timing gears in the engine, rather than a timing chain as used previously.
80 Military Jeeps used a variety of engines over the years, but the most unique has to be the 3-cylinder Cerlist diesel engine fitted to the FC-based M-series Forward Control trucks. This unique engine produced 85 hp and 170 ft-lbs of torque and was fuel efficient and durable. The army chose them because they were also multifuel engines that could run on diesel, kerosene, jet fuel, or gasoline.
Suspension and Brakes
81 Initially, the main use that the army had in mind for the Jeep was to serve as a scout/combat car capable of carrying a 50-caliber machine gun into battle, along with at least 3,000 rounds of ammunition for it. Those were part of the army specifications. Because of the weight of the ammunition and gun and the kick of the gun as it was fired, the rear floor area of the Jeep had to be heavily reinforced to withstand the strain, and the suspension had to be beefed up to carry the weight.
82 The Jeep MB’s axles were produced by Spicer, the same company that manufactured the transfer case and today is known as Dana Corporation. For the wartime Jeeps a Spicer Model 25 axle was used up front with a Spicer Model 23-2 in the rear. And talk about customer loyalty and longevity: To this day, Dana is still a major supplier of axles to Jeep.
83 Military Jeeps used a Ross Model T-12 cam and lever–type steering gear with a cam ratio of 14-12-14. Although early civilian Jeeps use essentially the same setup, these vehicles came with different tie-rod ends and a different mounting for the bell crank.
84 The military Jeep MB sat on a ladder frame that was built by Midland Steel, a company that was in business from 1893 to 2003. One of the easiest ways to tell a Willys MB from a Ford MB is to look at the front crossmember. The Willys Jeep used a round or tubular crossmember; the Ford vehicle used a U-section design.
85 Army Jeep brakes were four-wheel drums, 9x1.75 inches, mainly because disc brakes hadn’t been invented yet. The parking brake was a drum type working on the transfer case. The brakes were supplied by Bendix, a reputable firm still in business today. Jeep wheels were ruggedly built steel 16x4.5 inchers fitted with 6.00x16-inch tires. Understandably, whitewall tires were not available.
86 The military Jeep’s suspension was as tough as possible according to the engineering standards of the day and included heavy-duty semi-elliptic leaf springs at all four wheels. The vehicle’s ride was stiff, to put it kindly, but suspension failures were rare.
87 To provide important extra strength and robustness to the Jeep’s suspension system, heavy-duty anchor and shackle spring attachments were specified.
88 The Jeep MB maximum gross vehicle weight (GVW) was 3,250 pounds, and its maximum payload was 800
