John Deere 640D Grapple Skidder – Parts, Specs & Common Issues

Description:

The John Deere 640D Skidder is a high-powered, four-wheel-drive forestry skidder designed for aggressive skidding and log handling in rugged terrain. As a follow-up to the popular 640 and 640A/B models, the 640D offers increased horsepower, improved hydraulics, and upgraded operator comfort. Known for its robust grapple system and enhanced pulling torque, this machine is a staple in demanding timber operations.

Key Specifications:

• Engine: John Deere 6068T (6-cylinder turbocharged diesel)

• Horsepower: 145 HP gross

• Transmission: 6-speed powershift transmission with torque converter

• Brakes: Wet disc, hydraulically actuated

• Operating Weight: Approx. 26,000 – 28,000 lbs

• Grapple Opening Width: Up to 140 inches

• Tires: Standard 30.5L x 32 forestry tires

• Fuel Capacity: Approx. 70 gallons

Hydraulics:

• System Type: Closed-center, load-sensing

• Pump Flow: Approx. 45–50 GPM

• System Pressure: 2,500–2,800 PSI

• Functions: Blade, steering, grapple, and winch (if equipped)

Performance Features:

• High torque for efficient skidding on steep slopes

• Responsive grapple with strong clamping force

• Articulated frame steering for tight maneuverability

• Enclosed, climate-controlled ROPS cab with ergonomic joystick controls

Maintenance Essentials & Parts:

• Commonly serviced parts include grapple cylinder seal kits, transmission solenoids, and wet brake kits

• Steering orbitrol units and cylinder rebuild kits are often replaced after heavy use

• Hydraulic filter kits, engine filters, and fuel filters should be replaced per 200-hour intervals

• Grapple bushings and pins wear quickly under high loads

Common Issues and Fixes:

• Intermittent grapple function: Usually a result of worn hydraulic valve or low-pressure flow

• Transmission slipping in gear: Can be caused by solenoid failure or clutch wear

• Leaking steering cylinders: Common with age; replace with seal kit or full rebuild

• Brake fade or dragging: Typically caused by worn wet brake discs or clogged return line

Pro Tip:

The John Deere 640D serial number is located on the frame rail near the front left tire and also stamped on the engine block. Always confirm your serial before ordering parts.