Series 3 & 5J and 4 & 5U


The D2 is one of the most well-known and most-admired of the classic Caterpillar Diesel tractors. Production of the J series began in 1938 and ran until 1947 when the redesigned U series continued the line until 1958 when the D2 ceased production. They were the smallest diesel-powered crawler tractors that Cat produced and are a whole lot of fun today. There were many changes and refinements made to the D2 over the years. Let's start with the series designations. The J series was first, 3Js are the "narrow gauge" tractors and the 5Js the "wide gauge", these prefixes designated the width of the tractor from the center of track to center of track, 3Js are 40" on center, 5Js are 50". The U series followed the same protocol, with the 4Us being narrow and 5Us being wide. The big difference in the U series was the new D311 engine and other refinements as a result. The table below has more on what changed between the J and U series tractors. You can find the series designation on the serial number plates which are aluminium plates located in two places, at the top rear left hand side of the engine block and at the top left hand side of the rear of the transmission case.



D2's were put to many uses and there were many factory variations. You could find D2's on farms, in orchards and vineyards, logging, and on construction sites. There were versions that were specifically created for these applications. They were versatile, durable, and economical to operate for any of the tasks they were asked to accomplish. They are popular with people that have an interest in classic machinery due to their relatively small size and they can be transported (In the USA) with a pickup and a double axle trailer. Let's not miss the fact that they are still handy and can be found working in the field to this day. The D2 has earned its well-regarded status many times over with its ability to work tirelessly, and continue to provide today many hours of enjoyment for their owners.



How to Tell the Difference - the basics

D2 J SeriesD2 U Series
1938-1947 1947-1957
D3400 Diesel Engine D311 Diesel Engine
28.8 1525 rpm 32 D.H.P, 38 from 1954
Weight 6,850 lbs. Weight 6,870 lbs.
Main engine air cleaner Main engine air cleaner
located at front right of bonnet in front of operator at dash

Except for the early J series tractors the starting engine exhaust surrounds the diesel air intake manifold for quicker starting. Early J series tractors also had straight steering clutch levers.

Below is a list of machines made by year, model and serial number.



1938 1 2459 1 1259
1939 2460 4013 1260 2229
1940 4014 4952 2230 3549
1941 4953 6243 3550 5144
1942 6233 6789 5145 6153
1943 None None None None
1944 6790 7019 6154 7000
1945 7020 7629 7001 7839
1946 7630 7800 7840 9269
1947 7900 8600 9270 10561
1947 1 286 1 550
1948 287 1428 551 2199
1949 1429 2425 2200 4038
1950 2426 3750 4039 6403
1951 3751 4408 6404 8923
1952 4409 5584 8924 11285
1953 5585 6315 11286 13101
1954 6316 6864 13102 14700
1955 6865 7193 14701 15800
1956 7194 7385 15801 18200
1957 7386 7560 18201 18894

The members here at ACMOC have a wealth of knowledge on Caterpillar D2's and other Caterpillar crawler tractors and machinery.

Join today and you'll find digitized original manuals, historical photos, helpful members, and a wealth of information whether you have a D2 or are thinking you need one like the rest of us here at ACMOC, and trust us, you do need one.

Created by Kutrt Bangert and John Gaunt

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