Editor's note: This is an updated version of an article Tim King wrote entitled "Slat Grille Willys Exposed" and appeared in the Spring 2004 edition of Army Motors, no.107. Since the time of that writing, it became apparent to Tim that there were many people seeking information concerning the proper way to restore this model jeep. He thought it would help others in their jeep projects to re-publish this information in this updated format.
After Willys won the contract to build the standard quarter ton truck in WWII, they made various improvements to their pre-standardized version, the Willys MA. The first 25,808 vehicles off the assembly line starting from about November 1941 to March 1942 were built with a grille made from iron bar stock, resulting in what collectors call the "slat grille."
Willys adapted the idea of hiding the headlights under the hood from the Ford Model GP pre-standardized jeep. When Ford Motor Company was called into jeep production about March 1942, they decided that the wire grille configuration was too labor intensive and began to produce the standard 9 slot stamped steel grille which was just as strong but lighter in weight. The new grille design also incorporated the air deflectors to make a one-piece unit instead of all the individual radiator cooling baffles that had to be bolted to the inside the fenders and underneath the hood.
MB SLAT GRILLE BODY
Concerning the body, there are many differences to found there. Slat grilles before serial number 120,697 don't have a glove box. Because of the open space around the passenger toe board, the fire extinguisher is mounted there. Six round head screws that hold on the bracket on are visible from outside the vehicle on the passenger side. Later on the standard version the extinguisher was mounted above the driver's toe board because the glove box took away the necessary headroom.
The manufacturer's name in bold script is stamped into the left rear side of the back panel and you won't find a trailer light socket, fuel can carrier or fender mounted black-out driving light. These items weren't added until early to mid-1943. Because the early Ford and Willys jeeps both had the name stamped into the rear panel they are also know as "script jeeps" and you will also find the hood number in blue drab placed over the script name on the rear panel.
It should also be noted that the canvas top is an early style that has six cinch straps on the bottom rear. The later ones for use with the spare fuel can have a hole cut into the fabric for the fuel can strap to pass through and will have five straps.
The tool box lids are also different. Instead of having a long piano hinge with three screws to fasten the lid to the body, there are two small separate hinges per lid and instead of push-button openers there were locks keyed to use the same H700 key used for the ignition switch. The double hinges were used up to truck number 118,599. The fuel tank well is squarely cut and box shaped as later jeeps had a rounded off appearance most likely to save a sharp edge from hitting high obstacles.
MB SLAT GRILLE WINDSHIELD
The first 3,545 jeeps had a shorter windshield frame. It was discovered that many people were too tall to ride with a top installed on the vehicle so an extra two inches was built into the outer frame at the bottom where the sheet metal panel fits on. This area measures about 4" for the early frame and the later standard frame is 6". This measurement was once again increased by 2" for the civilian model CJ2A built from 1945 to 1949.
Slat grille jeeps used push-button fasteners on the windshield frame for the canvas top up to truck no. 164,554 and the windshield hold-down catches on the hood were arranged differently for the shorter windshield to be held in the down position. The inner windshield panels that hold the glass are universal, they even fit into the Ford GP frame. The standard (6") outer frame was equipped for the addition of a rifle scabbard. The clamps that fasten the windshield to the dash panel were made of solid brass as were the early GPW clamps. It's also appropriate to have single wiper assemblies that are not connected as the tandem wiper set didn't come out till sometime in 1944.
SLAT GRILLE INSTRUMENTS & DASH COMPONENTS
Early MBs had a solid black plastic Sheller steering wheel (WO A-6858) as shown in both TM-10-1186 and ORD 9 SNL G503 parts books however no information is given concerning when the change to the green plastic or steel spoke types was used.
Many differences exist with the instruments. First is the speedometer which is graduated in 5mph increments. It is the King-Seeley Corp. No. 40355 unit which was replaced by the Auto-Lite 10309 that is graduated in 1-mile per hour increments. Also common to the slat grilles is a 30/30 ammeter and a fuel gage that reads "GAS" instead of "FUEL."
The data plates are brass and the vehicle speed limit plate reflects a top speed of "65mph" instead of "60mph" for the standard version. The ignition switch is a H.A. Douglas Mfg. Co. product with a smooth round bezel that uses the H700 key. The switch in the GPW uses a round serrated bezel, an obvious difference. At truck 202,023 the keyed switch was dropped for the toggle ignition switch. The other controls are standard with the exception of not having a black-out driving light switch.
MB SLAT GRILLE SPRINGS & AXLES
The first jeeps were not equipped with the torque reaction spring as found on the driver's front spring of standard units. As jeeps were being distributed to using organizations, drivers were discovering an annoying and hazardous characteristic in jeep handling under emergency conditions. During heavy braking the jeep would steer by itself into oncoming traffic without any movement of the steering wheel. This condition occurred because the steering bell crank was mounted to the axle.
When the load of the vehicle was applied during braking, the front axle would twist forward due to deflection of the springs. This in turn would cause the bell crank to be pulled by the drag link and pull the wheels to the left. To combat this problem as cheaply and quickly as possible, a heavy iron spring leaf was added to the driver's side spring pack. It was fastened to the frame with a shackle at the rear and brought spring deflection down to a minimum.
The Jeeps steer to the left during heavy brake applications. Even so, if you are aware of the problem you can counter act it by a mild pull on the wheel to the right and drive safely even in emergencies. Normal driving and braking show no real differences. This problem was permanently corrected in the Civilian Model CJ2A and all models beyond by mounting the bell crank to the front frame cross member.
There is a date stamped on the differential carrier housing that should reflect a date that is a few days prior to your date of delivery if the axles are the original ones. To find this date, look at the cast axle housing facing the cover. You will find a cast boss on each side of the housing that is used to place the pins of a housing spreader tool. On the right pin hole around the outside flat area is the date. These jeeps should have eight front leaves to each spring and nine rear leaves.
MB SLAT GRILLE WHEELS
The same wheels used on pre-standardized jeeps were used on slat grilles up to truck no. 120,700. These are Kelsey-Hayes No. 24562 4"x16" drop center wheel with a solid disc center unlike later wheels which have four slotted holes around the center.
Early civilian jeeps had a wheel that would pass for this but was 4.50" in diameter. Trucks after 120,700 used the split, bolt-together style combat wheel with bead retainer (Kelsey Hayes No. 25692).
WILLYS MB AIR FILTER
The first trucks, including the Model MA up to 124,309, used the AC Spark Plug Co. Model A-183-40 pancake style oil bath air filter. This air filter was common to both early Ford and Willys jeeps. Filters used on Ford vehicles are said to be F-script marked. It was later replaced by the Oakes Model 613313 filter.
WILLYS MB RUBBER PARTS
Prior to the rationing of rubber during the war the jeep had many parts made of rubber such as the shifter boots and rubber fuel tank seals at the front and rear of the fuel tank sump which keep stones and dirt from wedging in between the tank and sump. Seat cushions were made of a sintered rubber material which was later dropped for wire springs and horse hair. There were also thin rubber grommets made to seal the tail lights in the rear body panel.
The hood was fitted with green rubber hood blocks up till truck no. 218,345 then the wood blocks with webbing were installed. I looked for truck serial numbers on the other items but was unable to find concrete evidence of when these changes were made except for the fuel tank stone guards which were dropped at truck 118599. Many such parts on the Ford GPW were made of non-rubber materials from the start such as leather shift boots and tar impregnated body grommets and seals, etc. Willys eventually used many of these same items.
MB SLAT GRILLE MISCELLANEOUS
Early jeeps had a different fuel tank with a narrow (2") opening using a cap the same size as used on civilian jeeps like the CJ2A. The bottom driver's seat pan was also different to accommodate the small cap. This tank was used until truck no. 174,739 which wasn't long after they began to mount spare fuel cans to the rear panel. The larger 4" cap was used and also had a lift out extension/strainer and of course the seat pan was changed to a larger opening.
The early exhaust system used a round style muffler and different exhaust hangers until truck no. 143,507 when the oval muffler was used. The battery tray remained the same as the Model MA until truck no. 120,700. The same was true of the brake line to the rear axle which was changed after truck no. 106,763.
Concerning the rear brake line on both the MA and early MBs, there is a small bracket fastened to the rear cross-member close to the driver's side frame rail. This is where the steel brake line was connected to the rubber hose which went to a junction block on the axle tube.
Later on, the brake tube went to the center of the cross-member and down to a junction block that was mounted on the top of the carrier housing to shield it inside the frame from getting tore out during off-road use.
The pintle hook used is the Holland Hitch Co. Model T-60-A without trailer safety chain eye bolts which weren't added till truck 158,372. The pintle hook on the GPW has a large script "F" on the passenger side.
Early door safety straps are distinguished from late style by a tan leather belt loop. Later production used canvas loops.
It's the author's hope that the information he has supplied here will help those restoring one of these rare jeeps. He had a great deal of help during the restoration of my jeep many accomplices in the hobby but especially from his close friend, John Geesink of Christchurch, New Zealand who has been an everlasting source of knowledge and encouragement.
We may not know how many slat grilles exist today, but more are discovered each year. Nevertheless, the numbers are still few and the prize will be a rare one when you finish restoring yours!
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