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The CJ-3A was produced for five model years, 1949 to 1953. Two other civilian Jeep models overlapped the CJ-3A's production. 1949 was the last year for the CJ-2A and in 1953 the CJ-3B became available. Unlike modern vehicles, the difference 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. These differences can be used to roughly date when a vehicle was manufactured. 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. To further complicate things Willys also had a manufacturing facility in California. Willys Service Bulletin 53-5 explains "the effective serial numbers given apply to changes made in vehicles assembled at the Toledo plant and do not apply to those assembled in our west coast plant". The CJ-3As military sibling, the M38, also went through many changes. Changes in the M38 seem to parallel a similar change in the CJ-3A with the military change happening first.I am collecting information about existing 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. To help by supplying information about your Jeep, please answer the questions near the bottom of this page.
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. Vehicle serial number tags are attached with 4 screws to the
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
with no regard for model year. Starting in 1951, and continuing through
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. See Willys-Overland
Production Figures 1945-61 on the CJ-3B page for a list of serial
numbers of Willys vehicles.
Body 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,
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. Early in the 1949 model year Willys began to build
bodies. Prior to
that American Central Manufacturing (ACM) manufactured the bodies.
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. Willys Service Bulletin #50-31 lists a change in the starter
and starter push rod at vehicle serial number (CJ-3A) 51911 which is in
the 1950 model year. The first
two starters are very similar, 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 key activated 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 the 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 from existing vehicles. 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 during the 1950 model year. Service Bulletin #50-31 states a different engine front plate was implemented at engine (3J)50551 for the new type generator and the new generator actually entered production at vehicle number (CJ-3A) 51951. Then in 1953 at vehicle serial number 453-GB1 17807 the generator and regulators were changed again 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 a copy of the Bulletin.
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 Master Parts
(copyright 1955) lists this change at vehicle serial number (CJ-3A)
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
a round differential cover while the model 44 cover has straight sides.
A larger diameter rear driveshaft appeared at about the same time as
rear axle change. Early CJ-3As used a 1-1/4" diameter rear driveshaft
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. The rear
driveshaft on the M38, the CJ-3As military equivalent, was changed from
1-1/4" to 1-3/4" diameter on 1/5/51 according to postings on The G503 Message Forums.
Colors The first CJ-3A windshield frames were painted the
body color. Most original vehicles after mid 1952 seem to have
windshield frames instead of body color windshield frames. This is
with the CJ-3B, which had black windshield frames. This change appears
at about vehicle serial number 452-GB1 20000.
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
Other Minor Changes
Click here for a list of other minor
changes that were made to the
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.
All comments are welcome
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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. Original soft top color, bow color and window size?
8. Are the hood blocks located equal distance from the hood center seam?
9. Does the tailgate top flange have cutouts? (see photo above)
10. Oil and temperature gauges, dial or lever type? (see photos above)
11. Is the horn button bakelite inside the steering wheel nut or a rubber cover over the nut? The rubber cover is often missing. (see photos above)
12. Does a push rod pedal, floor switch, dash button, or key activate the starter?
13. Are the transfer case shifters approx. the same height or is the front drive lever taller?
14. Does the transmission shifter have a bend in the middle or is it straight with the bend at the bottom?
15. Is the radiator side mount (grille mounted) or bottom mount (frame mounted)?
16. What is the vehicle serial number? (located on the tag screwed to the firewall near the air filter)
17. Is there a body tag, or holes for a tag, below the serial number tag? If so what is the body Number?
18. What is the engine serial number? (stamped on the boss between the water pump and cylinder head)
19. Is there a dimple in the air filter crossover pipe? (see photo above)
20. Does the air filter have a flat or dome shaped top?
21. Generator part #
22. Regulator part #.
23. Distributor part #
24. Starter part #
25. Does the engine block have the late large flange at rear of block? (see illustrations above)
26. What is the engine casting number? (passenger side just above the oil pan)
27. Is the rear axle a model 41 or model 44? (41 round cover, 44 straight sides)
28. Rear driveshaft small diameter (1-1/4") or large diameter (1-3/4")? (The front driveshaft is always 1-1/4" for comparison)
29. Left front fender splash apron bolted to frame? (see photos above)
30. Overall, is the vehicle original or modified on a scale of 1-10 with 10 being original?
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