Caterpillar 797F
The largest mechanical-drive haul truck Caterpillar builds — a 400-ton-payload truck powered by a single, enormous diesel engine rather than the diesel-electric drivetrains some rivals use at this size.
Overall height, top of ROPS (empty): 7.4 m — about 4.1× an average adult's height (1.8 m). The machine is always drawn at the same size here; the human figure is what actually scales.
01Overview
The largest mechanical-drive haul truck Caterpillar builds — a 400-ton-payload truck powered by a single, enormous diesel engine rather than the diesel-electric drivetrains some rivals use at this size.
02Purpose
Built to move the maximum payload a single mechanical drivetrain can handle, so a mine can haul more ore per truck without switching to a diesel-electric design.
03Historical Development
Caterpillar introduced the original 797 in 1998 specifically to compete at the top of the ultra-class haul truck market with a mechanical drivetrain, at a time when many rivals of similar size used diesel-electric drive. Successive versions — 797, 797B, and today's 797F — have kept that mechanical-drive bet while steadily raising engine output, culminating in the C175-20's 4,000 hp, about 450 hp more than its predecessor.
04Core Components
- Cat C175-20 engineA 20-cylinder, quad-turbocharged diesel displacing 106 litres — the core reason this truck can move at all.
- Torque converter & powershift transmissionCaterpillar's mechanical alternative to a diesel-electric drivetrain, chosen for serviceability and efficiency across the truck's full speed range.
- Final drivesMassive planetary reduction units at each rear wheel hub, delivering the last and steepest torque multiplication before the tyres.
- Dump bodyA reinforced steel bed engineered to survive a 400-ton payload of blasted rock being dropped into it, truck after truck, for years.
05How It Works
The C175-20 engine drives a torque converter and powershift transmission — the same basic chain as a bulldozer's, scaled up — through to final drives at the rear wheel hubs. Those final drives supply the last, steepest gear reduction, turning the engine's speed into the torque needed to move a fully loaded 620-plus-tonne gross weight up a mine's ramp grades, typically limited to around 10 percent specifically so trucks like this one can climb them loaded.
06Engineering Principles
Torque, not top speed, is what actually gets 400 tons of payload moving up a haul-road grade from a stop.
Power TransmissionFinal Drives & DifferentialsThe rear final drives deliver the last and largest torque multiplication in the whole driveline, right at the wheel hub.
EnginesFour-Stroke Diesel CycleThe C175-20's twenty cylinders each run the same basic four-stroke diesel cycle as a small generator engine, just twenty times over and turbocharged four times.
07Performance Characteristics
| Payload capacity | 400 short tons (363 t) |
| Gross machine weight | ~624 t loaded |
| Engine power | 4,000 hp (2,983 kW) |
| Engine displacement | 106 L |
| Top speed (loaded) | ~68 km/h |
08Notable Examples
- Escondida copper mine, ChileOne of the world's largest copper operations runs large fleets of ultra-class haul trucks in this size class.
- Athabasca oil sands, Canada797-class trucks haul oil-sands ore from shovel to processing across some of the industry's longest in-pit haul routes.
09Interesting Facts
- Its six tyres, at roughly 4 metres in diameter, are taller than most adult humans standing on each other's shoulders.
- The world's single largest haul truck by payload is actually the electric-drive BelAZ 75710, rated at 450 tonnes — the 797F remains the largest truck built around a purely mechanical drivetrain.
- A fully loaded 797F weighs more than a Boeing 737, moving under its own power on a dirt road.