The Caterpillar D2 tractor, produced from 1938 to 1957, holds a distinctive place in the history of American industrial and agricultural machinery. As one of Caterpillar’s smallest diesel-powered crawler tractors, the D2 became a symbol of reliability, versatility, and mechanical innovation during a transformative era in mechanized farming and construction. Its nearly two-decade production run reflects both its robust engineering and the widespread demand for compact yet powerful tractors capable of handling diverse tasks.
Dimensions
| Cat D2 | 3J (1938 - 47) | 5J (1938 - 47) | 4U (1947 - 57) | 5U (1947 - 57) |
|---|---|---|---|---|
| Length | 108 in (2743 mm) | 108 in (2743 mm) | 108 in (2743 mm) | 108 in (2743 mm) |
| Width | 52 in (1321 mm) | 62 in (1575 mm) | 52 in (1321 mm) | 62 in (1575 mm) |
| Height | 57.5 n (1461 mm) | 57.5 n (1461 mm) | 57.5 n (1461 mm) | 57.5 n (1461 mm) |
| Ground Clearance | 10 in (254 mm) | 10 in (254 mm) | 10 in (254 mm) | 10 in (254 mm) |
Introduced in 1938, the Caterpillar D2 emerged at a time when diesel power was still relatively new to smaller tractors. Diesel engines were more efficient, longer-lasting, and more economical than gasoline engines, but early diesel equipment was often large and cost-prohibitive. Caterpillar recognized a market opportunity: farmers, small contractors, and orchard operators needed a compact machine that retained the tough characteristics of larger crawlers. The D2, powered by Caterpillar’s two-cylinder D3400 (and later D311) diesel engines, delivered this combination of efficiency and durability. Although modest in size, typically weighing between 7,000 and 9,000 pounds depending on configuration, the D2 offered remarkable traction thanks to its crawler tracks, enabling it to operate effectively in soft soil, steep terrain, and other challenging environments.
Undercarriage
| Cat D2 | 3J (1938 - 47) | 5J (1938 - 47) | 4U (1947 - 57) | 5U (1947 - 57) |
|---|---|---|---|---|
| Track Gauge | 40 in (1016 mm) | 50 in (1270 mm) | 40 in (1016 mm) | 50 in (1270 mm) |
| Length of Track on Ground | 54.5 in (1384 mm) | 54.5 in (1384 mm) | 60.8 in (1545 mm) | 60.8 in (1545 mm) |
| Length of Track | 191 in (4846 mm) | 191 in (4846 mm) | 196 in (4978 mm) | 196 in (4978 mm) |
| Number of Shoes Per Side | 31 | 31 | 32 | 32 |
| Number of Track Rollers Per Side | 4 | 4 | 4 | 4 |
| Number of Carrier Rollers Per Side | - | - | 1 | 1 |
| Track Shoe Size (Standard) | 12 in (300 mm) | 12 in (300 mm) | 12 in (300 mm) | 12 in (300 mm) |
| Ground Contact Area | 1308 in2 (0.84 m2) | 1308 in2 (0.84 m2) | 1460 in2 (0.94 m2) | 1460 in2 (0.94 m2) |
Engine Details
| Engine Model | Cat D3400, 3.6L Diesel (1938 - 47) | Cat D311, 4.1L Diesel (1947 - 57) |
|---|---|---|
| Number of Cylinders | 4 | 4 |
| Displacement | 220 cu in (3.6 L) | 250 cu in (4.1 L) |
| Bore | 3.75 in (95 mm) | 4.00 in (102 mm) |
| Stroke | 5.00 in (127 mm) | 5.00 in (127 mm) |
| Horsepower (Drawbar) | 24.1 hp (17.7 kW) | 36.6 hp (27.3 kW) |
| Horsepower (PTO) | 27.5 hp (20.5 kW) | 29.0 hp (21.6 kW) |
| Horsepower (Belt) | 30.0 hp (22.0 kW) | 41.9 hp (31.2 kW) |
| Power Measured @ | 1525 rpm | 1650 rpm |
| Peak Torque | 125 lb ft (169.5 Nm) | 307.8 lb ft (417.3 Nm) |
| Torque Measured @ | 1050 rpm | 1052 rpm |
| Fuel Consumption | 2.1 gal/h (7.9 L/h) | 2.7 gal/h (10.2 L/h) |
| Cooling System | Liquid-cooled, thermostat | Liquid-cooled, thermostat |
| Oil Filter | Full flow metal element and own by-pass renewable cotton yarn type element | Replaceable paper element |
| Air Cleaner | Oil washed wire screen filter with collector precleaner | Oil washed wire mesh filter with precleaner |
| Aspiration | Naturally aspirated | Naturally aspirated |
Operational Specs
| Operating Weight | 7420 - 8536 lb (3365 - 3871 kg) |
| Operating Voltage | 6 V |
| Alternator (3J/5J Tractors) | 7 - 10 amps |
| Alternator (4U/5U Tractors) | 10 - 12 amps |
| Battery (3J/5J Tractors) | 6 V, 90 - 110 Ah, CCA 700 |
| Battery (4U/5U Tractors) | 6 V, 110 - 130 Ah, CCA 900 |
| Negative | Ground |
| Starter | 2-cyl gasoline pony motor / Electric starter |
| Caterpillar D2 Track Width | 12 in (300 mm) |
| Steering | Two hand levers controlling multiple disc clutches |
| Operator Station | Open operator station |
Transmission
| CAT D-2 | J Series | U Series |
|---|---|---|
| Type | Gear | Gear |
| Number of Gears | 5F / 1R | 5F / 1R |
| Clutch | Dry single plate clutch operated by hand lever | Dry single plate clutch operated by hand lever |
| Max Forward Speed | 5.1 mph (8.2 km/h) | 5.5 mph (8.9 km/h) |
| Max Reverse Speed | 2.1 mph (3.4 km/h) | 2.2 mph (3.5 km/h) |
| Max Drawbar Pull | 5903 lb (2677 kg) | 7413 lb (3362 kg) |
| Service Brakes | Contracting bands operated by two foot pedals one of which can be locked by latch | Contracting bands operated by two foot pedals one of which can be locked by latch |
Service Refill Capacities
| Fuel Tank Capacity (D2 J-Series) | 20 gal (76 L) |
| Fuel Tank Capacity (D2 U-Series) | 26 gal (98 L) |
| Gasoline Starting Tank | 1 gal (3.8 L) |
| Engine Oil Capacity | 2.75 gal (10.4 L) |
| Cooling System Capacity | 5.5 gal (20.8 L) |
| Transmission Oil Capacity | 5.5 gal (20.8 L) |
| Steering Clutch Compartments (each side) | 2 gal (7.6 L) |
| Final Drive Fluid Capacity (each) | 0.75 gal (2.8 L) |
| Oil Bath Air Filter Precleaner | 0.375 gal (1.4 L) |
The D2’s design evolved during its long production life. Early models, classified as the 3J series, were joined in 1947 by the improved 5U series, which incorporated engineering refinements such as enhanced engine power, upgraded cooling systems, and more comfortable operator controls. Caterpillar also offered various track widths and attachments, allowing owners to tailor the machine to specific applications.
This flexibility made the D2 popular across industries: farmers used it for plowing and cultivating; ranchers for dragging feed and clearing brush; construction crews for grading (dozer, traxcavator, etc), towing attachments, and site preparation; and the military for transport and light engineering tasks during World War II.
One of the D2’s most notable features was its reputation for reliability. Caterpillar engineered the tractor with simplicity and longevity in mind. Its rugged undercarriage, efficient fuel system, and remarkably durable engine enabled many units to remain in service decades beyond their initial purchase. The tractor’s hand-start gasoline pony motor used to start the main diesel engine became both a defining characteristic and a point of nostalgia among collectors, who view it as a hallmark of early diesel technology. The D2 also played a significant role in helping smaller farming operations mechanize, reducing labor demands during a period of agricultural modernization.
Production concluded in 1957 as Caterpillar introduced newer models with greater horsepower, improved ergonomics, and more advanced hydraulics. Yet the D2’s legacy endures. Today, it is celebrated among vintage machinery enthusiasts for its historical importance, compact charm, and mechanical ruggedness. Restored examples frequently appear at tractor shows, parades, and museums, serving as reminders of an era when dependable, human-scale machines reshaped the agricultural and construction landscapes across the world.
In retrospect, the Caterpillar D2 tractor stands as more than a piece of equipment - it represents a pivotal step in making diesel power accessible to small-scale operators. Its influence stretched well beyond its size, leaving an enduring imprint on mid-20th-century mechanization and earning its place as one of Caterpillar’s most iconic machines.
Production Numbers and Timeline Details
The Caterpillar D2 was built from 1938 until 1957 at Caterpillar’s plant in Peoria, Illinois.
- Over that nearly two-decade span, a total of 26,454 D2 units were manufactured.
- The production is usually broken down into two series: the J-Series (1938 - 1947), which accounted for about 19,161 units, and the U-Series (1947 - 1957), which comprised the remaining units.
- The 1947 introduction of the U-Series brought an updated diesel engine (the D311), which offered improved drawbar power and reliability compared to the earlier D3400 used in J-Series tractors.
- In 1953, further upgrades were made - including a longer final drive housing to simplify clutch replacement without pulling the engine, standardization of a track-carrier roller, longer tracks (32 shoes per side instead of 30), increased ground contact area, and larger fuel capacity (fuel tank raised from standard 20 to 26 gallons) - enhancing both performance and convenience.
- By 1957, production ceased. The trend toward larger, more powerful machines and changing market demands meant the small D2 crawler no longer fit into the modern lineup; it was effectively replaced by larger models.
Thanks to the substantial total production and the long production span including post-war years many D2s survive today, and the serial-number records (prefixes like “3J”, “5J” for J-series; “4U”, “5U” for U-series) are still used by collectors and restorers to date and authenticate machines.
Historical Price and Cost Context
Determining exact original prices for the D2 is difficult - record-keeping from that era is spotty, and values vary by region, optional equipment, and inflation. However, some credible sources and collector forums provide estimated figures:- A listing from 1946 for a 40-inch gauge D2 (with 12-inch tracks and standard seat) quotes a price of US $2,645.00.
- For a wide-gauge (50-inch) D2 configuration, observed sale data suggest that in September 1950, one was bought for around US $3,850, including “mud grousers” and a PTO option i.e. features beyond the basic tractor.
- Based on older dealer price lists for export markets, when adjusted from Australian pound to US dollar values (as was sometimes done for export), estimates suggest that a 1938 D2 might have sold for roughly US $2,400 - $2,500 (after accounting for shipping and exchange).
Taken together, those numbers place the D2 in the mid-range of affordability for mechanized farm or small construction equipment of its day. For a basic diesel crawler in 1940s America, a few thousand dollars represented a substantial investment - yet the utility, reliability, and durability of the D2 made it a sound value proposition for many small farms, orchards, and contractors.
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