The 6640 tractor has a four-cylinder diesel engine that produces 77.13 horsepower. The engine has a 304 cubic-inch piston displacement, a natural aspiration and a liquid cooling system. The bore is 4.40 inches and the stroke is 5 inches. The compression ratio offered by this engine is 17.5:1. Both two-wheel drive and 4WD models of this tractor feature the same Ford engine.
The Ford 6640 engine cooling system can hold 15.9 quarts of engine coolant. The gas tank holds 25 gallons of diesel fuel, which the tractor consumes at a rate of 4.7 gallons per hour. The 6640 agricultural tractor is capable of producing 67.18-horsepower drawbar, a measurement of pulling force.
The Ford 4WD 6640 weighs 8,135 pounds, which includes the weight of the tractor's optional rollover protection structure. This tractor's wheelbase between axles spans 93 inches. The tractor requires 7.50-inch 16-inch front agricultural tires and 16.9-inch by 30-inch rear agricultural tires. The tractor has differential hydraulic wet disc brakes. The hydraulic system designed into this tractor can pump hydraulic fluid at a rate of 18.2 gallons per minute.