Case 3550 Crawler Dozer Repair Manual

The Case 3550 crawler dozer was the largest track-type tractor ever produced by Case in the late 1970s and early 1980s. Engineered for large-scale mining, land clearing, and earthmoving projects, the 3550 combined a massive turbocharged diesel engine, heavy-duty power-shift transmission, and a reinforced undercarriage to compete with the largest dozers of its time. With an operating weight exceeding 110,000 lb and blade capacities up to 15 cubic yards, it was designed to deliver unmatched pushing power and productivity for Case’s biggest customers.

Generalities
The Case 3550 weighs approximately 110,000–115,000 lb, positioning it among the heaviest crawler dozers of its generation. Its large frame, wide track stance, and multiple blade options gave it the ability to move vast amounts of material efficiently on rugged job sites.

Engine
The machine is powered by a 6-cylinder turbocharged diesel engine with a displacement of approximately 19.1 L (1165 cu in). Rated at 350–375 gross horsepower (around 340 net), the engine produces over 1,050 lb-ft of torque at 1,400 rpm, providing the brute force necessary for mining and large-scale earthmoving.

Transmission
The 3550 is equipped with a 3-speed full power-shift transmission offering three forward and three reverse speeds. Capable of pushing heavy loads continuously, the transmission delivers smooth gear changes under load and efficient travel speeds of up to 6.5 mph forward and 7.5 mph in reverse.

Final Drives
Heavy-duty final drives were built to absorb high shock loads during heavy ripping and dozing, ensuring long service life even under constant full-power applications.

Brakes And Steering Differential
The machine uses hydraulic wet-disc brakes for reliable stopping power and low maintenance requirements. A differential steering system ensures maneuverability while maintaining traction, critical when working under heavy load conditions.

Undercarriage
The 3550 undercarriage includes eight bottom rollers and two carrier rollers per side, with 42–44 track shoes per side. Shoe widths range from 24 to 30 inches, and the track gauge provides stability for its heavy operating weight. Ground pressures average around 11 psi, with wider shoes available to reduce ground compaction.

Dozing Equipment Hydraulic System
A high-capacity hydraulic system with a 45-gallon reservoir powers the blade and auxiliary attachments. Blade choices include straight, semi-U, and full U blades with heaped capacities between 12 and 15 cubic yards, delivering excellent material handling performance.

Electrical System
The 3550 operates on a 24-volt electrical system with dual 12-volt batteries and an alternator, providing reliable starting power and supporting lights, diagnostics, and auxiliary electrical needs.

Key Highlights

• Production years: Mid-1970s – early 1980s
• Engine: 6-cyl turbo diesel, ~19.1 L (1165 cu in), 350–375 HP gross, ~340 HP net
• Max torque: ~1,050 lb-ft @ 1,400 rpm
• Operating weight: ~110,000 – 115,000 lb
• Fuel capacity: 180–200 gallons; Hydraulic capacity: ~45 gallons
• Transmission: 3-speed full power-shift (3F / 3R), speeds up to 6.5 mph forward, 7.5 mph reverse
• Blade options: Straight, Semi-U, or U blade; 12–15 yd³ capacity
• Track system: 8 bottom rollers, 2 carrier rollers, 42–44 shoes/side, 24–30 in shoe widths
• Ground pressure: ~11 psi (varies with shoe width)
• Brakes: Hydraulic wet-disc with differential steering
• Electrical: 24-volt system with dual 12-volt batteries and alternator