Case Terratrac 420 Crawler Dozer Repair Manual

The Case Terratrac 420 crawler dozer, manufactured between 1956 and 1958, was one of the compact crawler tractors in Case’s Terratrac lineup. Designed for farm, light construction, and grading work, the 420 offered operators a reliable and maneuverable dozer with the choice of gasoline or diesel power. Its simple open-operator design, rugged undercarriage, and optional hydraulic dozer/loader systems made it a versatile and durable machine in its class.

General Specifications
The Case 420 weighed about 7,000 lb in base configuration, with weight varying when equipped with dozer or loader attachments. Its compact footprint, 10-inch track shoes, and stable undercarriage gave it excellent balance and maneuverability for smaller-scale earthmoving operations.

Engine
Two engine options were offered: the Case G148, a 148 cu in (2.4 L) 4-cylinder gasoline engine, or the Case D148, a 4-cylinder diesel engine. The gasoline version delivered approximately 39 belt horsepower and 35 drawbar horsepower, while the diesel offered about 33 drawbar horsepower, providing adequate power for grading and light dozing tasks.

Fuel System
The fuel system was designed for simplicity and reliability, with the gasoline version using a ~17-gallon tank and the diesel version using ~18 gallons. Both versions provided sufficient fuel capacity for extended use in agricultural or light construction work.

Clutch
A dry-disc clutch system provided dependable engagement and power transfer from the engine to the transmission. The system was built to be rugged and simple, allowing straightforward servicing.

Transmission – Differential
The 420 used a 5-speed sliding gear transmission, with 5 forward and 1 reverse speed. Forward speeds reached about 4.8 mph, with reverse up to 2.7 mph, offering flexibility for grading and transport operations. Differential steering allowed precise maneuverability in tight working conditions.

Final Drive System
The final drive system was gear-driven and built for durability under continuous load. Its heavy-duty construction contributed to the machine’s reliability and long service life.

Track System
The track system consisted of approximately 41 shoes per side with 10-inch track width, supported by four bottom rollers and one carrier roller per side. With 11 inches of ground clearance, the crawler maintained stability while operating over uneven ground.

Electrical System
The 420 was originally equipped with a 6-volt electrical system, later commonly converted to 12-volt by operators for improved reliability. The system powered the starter and basic lighting.

Hydraulic System
The hydraulic system was optional and provided power for dozer blades and loader attachments. It offered smooth and reliable control, making the 420 capable of light grading, backfilling, and farm utility work.

Key Highlights

• Production years: 1956 – 1958
• Engines: Case G148 gasoline (39 HP belt / 35 HP drawbar) or D148 diesel (~33 HP drawbar)
• Displacement: 148 cu in (2.4 L)
• Transmission: 5F / 1R sliding gear; forward speed up to 4.8 mph
• Operating weight: ~7,000 lb
• Fuel capacity: 17–18 gallons
• Track system: 10-in shoes, 41 shoes per side, 4 bottom + 1 carrier roller
• Ground clearance: 11 in
• Blade: optional hydraulic dozer or loader, capacity suited for light work
• Electrical: 6-volt original, many upgraded to 12-volt
• Open operator station with simple controls