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M-38 Pilot Models

Photo from All-American Wonder Vol. III
by Fred W. Crismon

NEW  1/1/2009 In the time since this web-page was published some new photos of the Pilot Models have surfaced. The photos reveal that the pilot models were in a constant state of change as different features were implemented and tested. The new information shows that some previous assumptions are no longer valid. See the MVPA's magazine Army Motors #126 for the latest information.

By the end of the 1940s the US Army was ready to start replacing its aging fleet of W.W.II jeeps. It had been nearly 5 years since the last MB rolled off the assembly line and some vehicles were approaching 10 years of service. Many had seen extreme use during W.W.II, were then reconditioned, and would also see service in Korea. As popular as the jeep was from the beginning, Willys-Overland and the Army continued to experiment with many ideas for improvement. They tried to make it fly, turned it into a boat and used it as a farm tractor. On June 6, 1949 a contract for new design military Jeeps was awarded to Willys-Overland Motors, according to the Wall Street Journal. This was probably contract number W-20-089-ORD-4758 for 4000 units and spare parts. It included 6 Pilot models and regular production M-38s that were delivered though very early in 1951. The Mansfield News Journal (Ohio) reported that on December 15, 1949 Willys-Overland brought a "Pilot model" Jeep to the Detroit Arsenal for inspection by Army Ordinance Officials. This Jeep incorporated many new features developed at the request of the armed forces after studying reports on performance of combat vehicles. It was tested under the supervision of Willys-Overland's first vice president, Delmar G. Roos. The photo above was taken on December 22, 1949 with Delmar Roos on the left, and an Army Colonel on the right, standing behind what is likely to be this Pilot model. Some major improvements over the W.W.II jeep were a 24 volt electrical system, deep water fording capability, and commonality of components with other tactical vehicles. There were also provisions for quick starting in extremely cold weather and the entire powerplant assembly could be removed without so much as draining any fluids. The Traverse City Record-Eagle (Michigan) stated that "Six pilot models of the new jeep will be delivered to the army shortly after Jan. 1, 1950 for 60 day tests." The six Pilot models were referred to as MC-38 by Willys in the Maintenance Manual that was published specifically for them. This vehicle would evolve into the M-38 after many minor refinements were made.

The Pilot models are different than regular production M-38s and can
easily be identified by their combat wheels, headlight brush guards, door straps and full-floating rear axle, on an otherwise M-38 type vehicle. Upon closer examination many other unique characteristics are exposed. Many of these features can be seen in the MC-38 Maintenance Manual. We can also see that the Pilot models were built up from some CJ-3A components in addition to having legacy MB features. The full-floating rear axle and combat wheels were carried over from the W.W.II jeep to the Pilot models but were not incorporated in the M-38 vehicles. Colonel J. E. Engler, chief of the Army's automotive branch, said during a House Appropriations Committee hearing in 1951 that semi floating rear axles were used in place of full floating axles for cost savings. Some of the Pilot models had oil cans and grease guns mounted in the engine compartment and tire pumps under the rear seat. Pilot models also had different headlight guards than M-38s. Cylindrical "Can" and "Vertical bar" type guards are seen in Pilot model photos while "Diagonal bar" guards were used in regular production.

Headlight guards in order of appearance; Can, Vertical bar and Diagonal bar.

The cowl battery box lid was hinged on the driver's side for Pilot and at the front for production models. The center rectangular area below the windshield is noticeably smaller on Pilot model Jeeps because the vent hole appears to be embossed, but not punched out. Production M-38s had a cover that was bolted over the punched out opening and CJ-3As used a hinged vent lid on the opening. In production a Cuno serviceable oil filter was used in place of a conventional replaceable element type canister filter. Pilot model hood blocks were not evenly spaced from the hood center. This was a carryover from CJ-2A civilian Jeeps where the offset was necessary to clear the high mounted wipers. In production the hood blocks were evenly centered since the wipers were now mounted below the glass.
Another unique Pilot model feature is the axle vent plumbing. Both axle housings were connected to the underwater ventilation system along with the other gearboxes and reservoirs. Some of the fittings and lines inside the right frame rail can be seen in the photo to the right. The vent system was connected to the air filter housing to reduce water intrusion when submerged. Strangely, in production the axle housing portion of the ventilation plumbing was eliminated and replaced by simple check valve fittings at each axle. Also visible in the photo is the chaff deflector portion of the front propeller shaft guard. These front and rear propellor shaft guards did not make it to production either. It is likely that many of these new features were omitted to lower the final price, as was the full floating rear axle.
The extra weight of new features, combined with taller 7.00x16 tires and 4.88 axle ratios must have seriously taxed the output of the 60 horsepower flathead engine that had been acceptable in the lighter weight MB jeep. To help regain some lost power M-38s were fitted with a 5.38 gear ratio.

It seems that each of the 6 Pilot models were slightly different. The Maintenance Manual sums it up with this statement "It must be recognized that these vehicles were subject to changes during construction and in some cases optional construction used for test purposes." By the end of the test period some features were accepted, some eliminated and some modified for the final product, the M-38.

nique features listed by hood number
The Maintenance Manual reveals USA Registration Numbers (hood numbers) for the 6 pilot models as 2368159 through 2368164.

This Jeep has no hood number. It is equipped with cylinder type headlight guards or “headlights in a Can”. It also has a left side blackout driving light, and screws on the side of the hood for a grease gun mounting bracket. There are no front lifting shackles or winch installed. Since this vehicle appeared late in 1949, before the "6 Pilot Models" were delivered, maybe it should be referred to as a prototype.

Click image above for a larger view

Click image above for a larger view
The next two photos show another Jeep that does not have hood numbers but does have a Gar Wood winch and front lifting shackles. It also has civilian type side drain holes, civilian side step attachment holes, Can type headlight guards, left side blackout driving light and screws on the left side of the hood for a grease gun mounting bracket. The slave cable receptacle on right fender is recessed inside the hood so it would be difficult to remove the cover without opening the hood. There is no fuel filler guard installed.

This lower
image is the same Jeep as above. It appears in the Pilot Model Maintenance Manual. Compare the position of the wiper blades and the winch cable. They are in exactly the some positions in both pictures. Look closely at the headlight guards in the illustration. They appear suspiciously retouched. At this point in time the Army must have decided to use bar type headlight guards so Willys reflected that change by altering the illustration.

Perhaps this is another prototype?

Hood number 2368159 has a large winch fitted; it looks similar to a Ramsey. Also seen are Vertical bar headlight guards, a fuel filler guard, left side blackout drive lamp and screws on the side of the hood for a grease gun mounting bracket. There are no body side drain holes.

No photo available

Hood number

Hood number 2368161 does not have a winch. The slave cable receptacle is mounted in the right front wheelwell area where it could easily get covered with mud. This Pilot model has Vertical bar headlight guards and front lifting shackles but there are no side drain holes in the body. The second image appears to be a retouched photo of the same Jeep without the canvas top.

No photo available

Hood number 2368162

Apparently hood number 2368163 was never delivered to the Army. It has a Braden capstan winch, slave cable receptacle mounted in right front wheelwell area, Can type headlight guards, drain holes are in the floor not in the side of the body, threaded front axle hub covers, blackout driving lamps on both front fenders, a grease gun mounting bracket mounted to the hood and has lifting shackles. Absent is a fuel filler guard.

Hood number 2368164 has the slave cable receptacle mounted on the top of the fender but not recessed like the prototype model. There are no side drain holes, but it does have lift shackles, Vertical bar head light guards, fuel filler guard, screws on the side of the hood where a grease gun mounting bracket is installed.

Apparently some Pilot models were used by the Army for testing purposes even after regular M-38 delivery started. This is evidenced by the 3 photos of 2368164 (above) showing the same vehicle in different configurations.

To the right are additional Pilot model photos. Unfortunately there are no hood numbers visible so we don't know which vehicle they are. One Jeep has a Gar Wood winch but no lifting shackles, unlike the previous Gar Wood winch equipped Jeep. The lower Jeep certainly looks well used judging by worn tires and scuffed front bumper. It is unique in that it has a Ramsey model 50 winch mounted. The model 50 is smaller and lighter than most of the other winches that were tested and was selected as the winch to be factory installed on M-38s.

Pilot models were a combination of MB, CJ-3A and "new M-38" components. It appears the US Army was trying to create the perfect Jeep with the M-38, but they still had to be concerned with the price.
Finally in September of 1950 the Army started taking delivery of the first M-38s, approximately 1 year and 3 months after the first contract was awarded.

Thanks to... All-American Wonder Vol. III by Fred W. Crismon, Harold West, Wes Knettle, Jan Hogendoorn, David Uhrig, and the current owner of MC 10005.

Bob Westerman

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