Dating A CJ-3A

By Bob Westerman


The CJ-3A was produced for five model years, 1949 to 1953. Two other civilian Jeep models overlapped the CJ-3A's production. During the 1949 model year the CJ-2A was also available and in 1953 the CJ-3B became available.  Unlike modern vehicles, the change between CJ models was not distinct. The CJ-3A had many features similar to the late CJ-2As. Likewise the late CJ-3A had some of the new characteristics of the CJ-3B. Therefore all CJ-3As are not even the same. The commonly accepted description of the CJ-3A seems to apply only to the mid production vehicles. The lack of factory parts information from the CJ-3A time period makes it very difficult to decide if and when changes were made. Much information has been obtained from the CJ-2A and CJ-3A Parts List (copyright 1949) and the 1945-1949 Master Parts List (copyright 1955). Many of the listings in the 1945-1949 Parts Master List are for  years later than 1949. Both manuals contain some errors and omissions.

I am collecting information about the CJ-3As to help determine when changes took place. Because anything could have happened to these vehicles in the 50+ years since they were manufactured, a large sampling of vehicles is necessary to determine which assumptions are valid. From the information I have collected to date the following differences are appearing. This information is preliminary and it changes rapidly as new information is received from enthusiasts like you.

Vehicle Serial Numbers The CJ-2A/CJ-3A Parts Book (copyright 1949)  states that the beginning of production vehicle serial number is 10001 with engine serial number 10001. Serial number tags are attached with 4 screws to the engine side of the firewall near the air filter. The vehicle serial number had a prefix of CJ-3A for the first 2 years of production. During this time the serial numbers continued to climb with no regard for model year. Starting in 1951, and continuing through final production, a new format was used. The prefix was changed to indicate the model and model year and the serial number itself was reset to 10001 at the beginning of each model year.

Body TagBody Tags The earliest 1949 CJ-3As have a body number tag below the serial number tag on the firewall. Later in 1949, and for the remainder of production, the body tag was eliminated. Body tag numbers are initially close to the vehicle serial number and then skew to about 1200 less than the vehicle serial number. What does this mean? How could there be less bodies than vehicles? The body tag to the left is from a 1949 CJ-3A, thanks to Andy Testo for the photo. During late 1948 to early 1949 Willys began to build their own bodies. Prior to that American Central Manufacturing (ACM) manufactured the bodies. Were the body tags eliminated when the body building was brought in-house?


Late rear flangeEngine serial number locationEngine changes The engine serial number is located on the boss just to the rear of the water pump; click on the engine serial number illustration at the right for the location. The first CJ-3A engine serial number should be 3J10001 and then increase through out the remainder of production. Serial number lists of other models of Willys vehicles indicate that engine serial numbers increase at a faster rate than the vehicle serial numbers. This "skew" is probably due to engines being pulled from stock for other uses, such as replacement engines. Existing original CJ-3A engine serial numbers initially increase as expected, but then in 1950 and 1951 the skew becomes negative by approximately 2000. Then in 1952 and 1953 the engine numbers climb again as expected. The negative skew would indicate there are fewer engines than vehicles. What caused the engine serial number difference in 1950 and 1951 to account for a discrepancy of several thousand engines? In 1952 the engine block was changed to one with a larger flange at the rear. The 1965 Service Manual states that this was done at engine serial number 130859. At this time the timing marks were moved to the front cover because the large flange covered the existing timing inspection hole location. The bellhousing was also changed to accept the new starter introduced here. The illustration to the left, from the 1965 Universal Service Manual, shows the late large flange engine block with the early starter and timing hole. The early block casting number is 641087 and the late block casting number is 804380. There are also a few transition blocks with casting number 641087 and the large flange. Block casting numbers are found just above the oil pan on the passenger side.

Starters and Generators Starter and generator numbers are found on a tag that is riveted to their housings. Three different starters were used. The first vehicles used the Autolite MZ-4137. In mid 1950 the starter was changed to MZ-4162, according to Autolite manuals. The 1945-49 (copyright 1955) Parts manual lists a change in the starter push rod at vehicle serial number 51911. This is likely to be the serial number where the starter change took place. Both of these starters are interchangeable, are activated by a foot pedal linkage, open nosed, and use a 124-tooth flywheel. The third starter is Autolite MCH-6203. This starter is a key start with a solenoid mounted to the top of the starter and is the closed nose type. It uses a 129-tooth flywheel. The 1965 Universal Service Manual states that this third starter was put into production with vehicle serial number 30973 and, on a different page, engine serial number 130859. By adding the prefixes 452-GB1 to the vehicle serial number and 3J to the engine number, the result is vehicle 452-GB1 30973 with engine 3J130859. These are credible numbers for a 1952 CJ-3A and this data fits perfectly into the information collected to date. The engine block change to the larger rear flange also occurred at this serial number.

The generator changed from the Autolite GDZ-4817 to Autolite GDZ-6001, most likely during the 1950 model year. Then at vehicle serial number 453-GB1 17807 the generator and regulators were changed to provide a greater output. According to Service Bulletin 53-5 this generator provided a nominal 45 amp output. This last generator may have been an Autolite GGW-4801 or GGW-7404. Thanks to Bill Norris for copies of the Bulletins.

Differential CoversAxles and Driveshafts One of the common improvements associated with the CJ-3A is the model 44 rear axle. The model 41 axle was actually used in the 3A until the end of the 1950 model year. The 1945-49 parts book (copyright 1955) lists this change at vehicle serial number 62488 (very late 1950 model year). On the Classic Willys Message List Todd Paisley stated that Engineering Release #6427 Rear Axles (Spicer) - Change from Spicer Model 41 to Model 44 was started on October 31, 1950 and and implemented on November 30, 1950. The rear axle can be identified by the shape of the differential cover (see photos at left). The model 41 axle uses a round differential cover while the model 44 cover has straight sides.

A larger diameter rear driveshaft appeared at about the same time as the rear axle change. Early CJ-3As used a 1-1/4" diameter rear driveshaft while the later 3As used a 1-3/4" diameter rear driveshaft. I have not been able to pinpoint when the change was made because during the 1951 model year I am seeing both small and large diameter driveshafts randomly. By 1952 all driveshafts are large diameter.

Radiator The first CJ-3As utilized a bottom-mounted radiator, like the 2As. The bottom of this radiator was bolted to the frame crossmember and had a rod that extended between the bracket on the radiator top tank and the firewall. The side mount radiator was bolted to the grill on both sides instead of the frame, and lacked the top connecting rod. The change to a side mounted radiator, according to the 1945-49 Master Parts list (copyright 1955), was after CJ-3A 21656. Keith Buckley also added that the Air Deflector portion of the grille changed from 22 gage to 18 gage at this time. This logically was done to support the extra weight of the radiator. Surveys of existing vehicles is showing the possibility of a short run of  bottom mounted radiators after the side mounted radiator had been put into production.

Hood The early CJ-3As had short hood blocks and they were not equidistant from the hood center seam. In late 1950 to early 1951 the hood blocks changed to the taller type associated with the 3A and their location was equal distance from the hood centerline. This change appears roughly before serial number 451-GB1 17000.

Horn Button
Horn buttons change from the button inside the steering wheel nut to the rubber cover over the nut type. This change is appearing at approximately the same time as the 1950 to 1951 model year change. The 1945-49 part book lists this change at vehicle serial number 57215 (1950). Surveys of actual vehicles show that both types of buttons were used into 1951.  The rubber cover is often missing from the late style.

 Early Horn Button      Late Horn Button    Late button w/o cover  

Early horn button inside nut             Late button with rubber cover           Late style with cover missing

Tailgate  A minor change was made to the tailgate in mid 1951. The M38, a sibling of the CJ-3A, required four cutouts in the top flange of the tailgate to allow for rear seat bracket and spare tire carrier attachment. This modified part carried over to the civilian Jeep although it was not necessary on the CJ. The photo below shows a late tailgate with 3 of the 4 cutouts visible. The 4th cutout is the longer oval type on the far left side of the tailgate. See the excellent article, Tailgate Reading, on the CJ-3B Page for more information about this change.

Tailgate Notches

Canvas Body Top Willys parts manual illustrations show the CJ-3A with a 7 piece canvas top and metal framed windows similar to the CJ-2A. The 1945-49 parts book (copyright 1955) states there is a "New front top kit with larger curtain lights and eliminating window frames. New door assemblies and side curtains may be serviced for the old type with smaller windows in pairs only." Unfortunately the serial number listing for this change was left blank so we do not know when this change took place. The Metal door frames were also changed to make room for the larger windows. This was done by relocating the diagonal brace below the door handle. The CJ-3B continued to use the larger window type top.


Colors The first CJ-3A windshield frames were painted the body color. Most original vehicles after mid 1952 seem to have black windshield frames instead of body color windshield frames. This is consistent with the CJ-3B, which had black windshield frames. This change appears at about vehicle serial number 452-GB1 20000.

It seems that most CJ-3As have been repainted since they left the factory. Original body color paint can often be found in areas where the re-painter missed.  Look under the dash, behind bolted on components like the serial number plate, and low on the firewall where it is oily.

Jim Allen's book, the Illustrated Buyers Guide, Jeep shows the following vehicle colors available for the CJ-3A years.
1949 Harvest Tan, Pasture Green, Harvard Red, Michigan yellow, Princeton Black, Picket Gray, Luzon Red, Normandy Blue, Olive Drab
1950 Harvest Tan, Pasture Green, Harvard Red, Michigan yellow, Princeton Black, Picket Gray, Luzon Red, Normandy Blue, Olive Drab
1951 Harvest Tan, Pasture Green, Harvard Red, Horizon Blue (Farm Jeep only), Michigan yellow, Princeton Black, Picket Gray, Luzon Red, Normandy Blue, Olive Drab
1952 Hampshire Green, Harvest Tan, Pasture Green, Harvard Red, Horizon Blue (Farm Jeep only), Michigan Yellow, Picket Gray, Luzon Red, Normandy Blue, Olive Drab
1953 Cadet Gray, Hampshire Green, Saber Rouge, Woodstock green.

Sherwin-Williams and Dupont paint chip catalogs from 1949 to 1951 list available Civilian Jeep colors as Emerald Green, Luzon Red, and Potomac Gray. Horizon Blue is also listed only for the 1951 Farm Jeep. A 1951 Ditzler Bulletin lists colors for Universal Jeep, Farm Jeep, and Jeep Tractor as Luzon Red, Emerald Green, Potomac Gray, Horizon Blue and Universal Beige. For 1952 Dupont shows Hampshire Green Metallic as the only Jeep (CJ) color. Ditzler has Hampshire Green and Horizon Blue. In 1953 Dupont, Rogers Paint Products, and Ditzler paint chips only have Woodstock Green listed. A Ditzler Bulletin dated July 7, 1953 adds Cadet Gray and Saber Rouge.

With all this conflicting information it is hard to decide what colors were actually used. The following data is compiled from owners of existing CJ-3As as of  10/04.
1949  20% Green, 16% Red, 5% Black, 2% Tan, 2% Gray
1950  32% Red, 10% Green, 5% Black, 2% Gray
1951  18% Red, 16% Green, 6% Gray, 4% Blue, 2% Yellow, 2% Black
1952  25% Green, 19% Red, 9% Blue, 3% Yellow
1953  22% Red, 22% Blue, 17% Green, 17% Gray
The remaining percentage for each year is unknown.

Original wheel colors are difficult to find. The wheels on many vehicles have been replaced since wheels are easily exchanged. The "Gray Jeep" as seen on the CJ-3B Page has reddish orange wheels (Sunset Red?) so we can assume that in 1951 there were several different wheel colors depending on the body color. Did the last 3As use just black or white wheels like the later CJs?

The 1945-49 parts book (copyright 1955) lists available replacement seat colors as Slate Gray, Olive Drab, Red Barcelona and Dark Gray.

Canvas top replacement parts were only available in Slate Gray according to this manual.

From the G503 CJ Technical Knowledge Base comes this information; Engineering Release #5248 Gas Tank Assey. (Painted Black) - Revise Paint Spec. From body Color to black Enamel started on  1/27/49 and issued 2/15/49. This indicates that the early 1949s had body colored fuel tanks. The change to black fuel tanks may have occurred at about the same time as the body serial number tag was eliminated. 

More data is needed to confirm these findings. Much of this information does not seem to be written down anywhere so your input is very important to document the changes. If you own a CJ-3A, or have any information about the 3As, please fill out the following survey and e-mail it to The answers to any of the questions is helpful even if your Jeep has been modified or you can not answer all the questions. Your input can help record the history of the 3A.

I would like to thank everyone who has helped by providing information. There are far too many people to name. All the people who took the time to provide data about their CJ-3A deserve credit as this couldn't be done without them. Special thanks to Harold West for help with the data and ideas about how to analyze the information.

More information and all comments are welcome
Bob Westerman

Willys CJ-3A Questions
Please answer the questions as your Jeep was originally equipped.
1. Owner Name
2. What is the model year of the Jeep?
3. What is the original body color?
4. What is the original color of the windshield frame?
5. What is the original color of the wheels?
6. What is the original color of the gas tank?
7. Are the hood blocks located equal distance from the hood center seam?
8. How tall are the hood blocks?
9. Is the horn button bakelite inside the steering wheel nut or a rubber cover over the nut? The rubber cover is often missing.
10. Does a push rod pedal, floor switch, dash button, or key activate the starter?
11. Is the radiator side mount (grille mounted) or bottom mount (frame mounted)?
12. What is the vehicle serial number? It is located on the tag screwed to the firewall near the air filter.
13. Is there a body tag, or holes for a tag, below the serial number tag? What is the body Number?
14. What is the engine serial number? It is located on the boss just above and behind the water pump.
15. What is the cylinder head casting number?
16. Generator part #
17. Regulator part #.
18. Distributor part #
19. Starter part #
20. Does the engine block have the late large flange at rear of block?
21. What is the engine casting number? (passenger side just above the oil pan)
22. Is the rear axle a model 41 or model 44? (41 round cover, 44 straight sides)
23. Rear driveshaft small diameter (1 1/4") or large diameter (1 3/4")?
24. Wheels welded or riveted construction and 15" or 16" diameter?
25. Does the tailgate top flange have cutouts? See Tailgate Reading, on the CJ-3B Page for more information.
26. Original soft top color, bow color and window size?
27. Overall, is the vehicle original or modified on a scale of 1-10 with 10 being original?