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 Series||D2 U Series|
|D3400 Diesel Engine||D311 Diesel Engine|
|28.8 D.H.P.at 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.
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