The JD 640D Skidder is a type of heavy vehicle used to haul felled trees out of logging areas. Depending on the type of skidder, they are equipped with either cables or grapples. The JD 640 is a cable skidder. Cables skidders haul away logs using cables controlled by winches. Winches are mechanical devices used to wind-in and wind-out cables.
Core features of the JD 640D Skidder include a 90 kilowatt turbocharged John Deere engine, automotive-type position-responsive steering, articulated frame steering and oscillating front axle. They also include a power shift transmission, a hydraulically controlled winch, enclosed self-adjusting wet-disk power breaks and hydraulically-powered differential locks on both the front and rear axles. Optional components include a stacking blade and a trail-building blade.
The engine of the JD 640D Skidder is a 4-stroke cycle, turbocharged diesel engine. Its features include six cylinders, a displacement of 414 cubic inches, a maximum net torque of 358 pounds per foot at 1300 RPMs, a compression ratio of 16.8 to 1, a blower cooling fan, pressure system lubrication with a full flow filter, a dry air cleaner, a 12 volt electrical system with a 42 amp alternator and two batteries with 320 minutes of reserve capacity.
The transmission is a power shift transmission. It has planetary gears and hydraulically actuated wet-disk clutches and brakes. The transmission provides eight speeds moving forward and four speeds moving in reverse. It comes with an air to oil cooler and is controlled using a single lever that is found on the main console.
The skidder comes with S4 series axles, bottom guards, a cushion seat with suspension and position adjustment, engine sideshields, an exhaust with a rain deflector and an alternator warning light. It also comes with a canopy with brush screens and limb risers, a foot throttle, a heavy-duty starter, a horn, standard gauges, an integral log bumper, a two-position hinge locking bar, a key switch with a push-button safety start, a muffler, a solid-state voltage regulator, a log arch with a multi-position roller and an engine oil pressure warning light.