Caterpillar 550

The Caterpillar 550 is a wheel harvester, a single-grip cut-to-length forestry machine built to fell, delimb, and buck timber in one pass. Engine varies by production series: early build used the Cat 3126 / 3126 DITA turbocharged diesel, later Tier III production switched to the C7 ACERT rated around 147 kW (197 hp) at 1800 rpm; both engines land near the same net output and share the same 7.2 L displacement. Operating weight varies by configuration, from roughly 15.4 t (34,000 lb) for the bare wheel-harvester chassis up to about 21.3 t (47,040 lb) with a harvester head and full fluids fitted. Production years vary by source, running roughly late 1990s through mid-2000s. The 550 rides on a wheeled bogie-axle undercarriage, a gear-drive front bogie with differential lock and a straight rear axle, both on wet disc brakes, instead of a track chain, and uses a pendulum-arm boom suspension to keep the head following ground contour on slopes. It was offered with a telescoping boom reach from about 8.2 to 10.1 m (27 to 33 ft) and different harvester head options, and sat as the smallest machine in Cat's concurrent 550/570/580 wheel-harvester family under the Cat Forest Products Group.

The clearest documented change across the 550's run is the engine swap from the 3126 DITA to the Tier III C7 ACERT, driven by emissions rules rather than a horsepower increase, since both land near 197 hp. No factory-published serial break marks that changeover, so confirming which engine sits under the hood means reading the engine tag rather than trusting the model plate or a parts-book guess. No direct successor model is documented for the 550; Cat kept running the 550/570/580 wheel-harvester line and later broadened its forestry equipment lineup through other acquisitions, but no source ties a specific follow-on machine to this model number. In the used and parts market, the 550 still turns up on contractor lots because its wheeled bogie-axle undercarriage is cheaper to run and repair than a tracked harvester, and its 3126/C7 drivetrain shares wear parts with other common Cat industrial engines still in service. Buyers and parts counters need to pin down engine generation and attachment configuration before ordering filters, injectors, or bogie axle components, since the two engine families and different operating weights do not interchange.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.