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For years, Cat® knuckleboom loaders have been known for superior hydraulic performance in tough logging applications, heavy-duty boom and structures that are built to last, and fuel efficient engines that provide impressive torque characteristics. A complete factory installed delimber slasher (DS) package ensures you have the right grapple, delimber, and trailer combination for any job.


  • Gross Power 173.0 HP 129.3 kW
  • Engine Model Cat C4.4 ACERT Cat C4.4 ACERT
  • Gross Power - 1,800 rpm 173.0 HP 129.3 kW


  • Operating Weight 36500.0 lb 16556.0 kg
  • Counterweight 1440.0 lb 653.0 kg
  • Operating Weight - Without Grapple 36500.0 lb 16556.0 kg

Operating Specifications

  • Knuckleboom Length 32.0 ft 9.8 m
  • Swing Speed 9.5 r/min 9.5 r/min
  • Note *Theoretical *Theoretical
  • Maximum Reach - Standard Boom 32.0 ft 9.8 m
  • Tail Swing 108.2 in 2750.0 mm
  • Swing Torque* 73800.0 ft·lbf 100360.0 N·m
  • Swing Bearing - Diameter - Ball Path 43.5 in 1105.0 mm

Service Refill Capacities

  • Hydraulic Tank 80.0 gal (US) 302.0 l
  • Fuel Tank 100.0 gal (US) 378.0 l
  • Engine Oil 2.1 gal (US) 8.0 l
  • Swing Drive 2.6 gal (US) 4.0 l
  • Cooling System 7.5 gal (US) 29.0 l
  • DEF Tank 5.0 gal (US) 19.0 l

Hydraulic System

  • Hydraulic Pressure - System 3625.0 psi 24994.0 kPa
  • Cylinders - Stick one one
  • Hydraulic Pressure - Swing 3625.0 psi 24994.0 kPa
  • Hydraulic Oil Flow at 1,800 rpm 230/230 L/min (60/60 gal/min) 230/230 L/min (60/60 gal/min)
  • Cylinders - Stabilizers four four
  • Cylinders - Main one one


  • Stabilizer Spread - Maximum Down Reach 166.8 in 4237.0 mm
  • Stabilizer Pad Size 508 × 711 mm (20 × 28 in) 508 × 711 mm (20 × 28 in)
  • Stabilizer Reach Below Grade 15.5 in 394.0 mm
  • Height - Top of Cab 159.1 in 4041.0 mm
  • Stabilizer Spread - Grade 183.8 in 4670.0 mm
  • Note 579D dimensions are on suspension trailer. 579D dimensions are on suspension trailer.


  • OFPS OFPS cab meets SAE J2267 OFPS cab meets SAE J2267

Shipping Dimensions - Mounted Trailer

  • Width 101.3 in 2573.0 mm
  • Height 159.1 in 4041.0 mm

GLK Series Grapples - GLK48

  • Height - Open - Excluding Rotation 45.1 in 1146.0 mm
  • Weight - Excluding Rotation 1407.0 lb 638.0 kg
  • Close 4.5 in 114.0 mm
  • Height - Open - Including Rotation 66.0 in 1685.0 mm
  • Note All specifications are approximate. All specifications are approximate.
  • Area (tip to tip) 3.0 ft² 0.91 m²
  • Open 48.0 in 1219.0 mm
  • Weight - Including Rotation 1907.0 lb 865.0 kg

GLK Series Grapples - GLK55

  • Weight - Excluding Rotation 1411.0 lb 640.0 kg
  • Area (tip to tip) 3.8 ft² 1.15 m²
  • Close 5.0 in 127.0 mm
  • Weight - Including Rotation 1911.0 lb 867.0 kg
  • Open 54.0 in 1372.0 mm
  • Height - Open - Including Rotation 68.0 in 1724.0 mm
  • Height - Open - Excluding Rotation 46.7 in 1186.0 mm
  • Note All specifications are approximate. All specifications are approximate.


  • The Cat® C4.4 ACERT™ U.S. EPA Tier 4 Final engine provides equivalent power (129.3 kW/173 hp) and optimized performance compared to C Series while minimizing overall fluid consumption
  • Advanced controls manage pump and engine interface to optimize performance and fuel efficiency
  • Leading hydraulic multi-functioning capability enables operator to lift, swing, and rotate grapple simultaneously without impairing performance


  • Auto idle minimizes fuel consumption when machine is on and not actively working
  • High capacity cooling system only pulls in cool external air to maximize efficiency
  • Electrically controlled variable speed fan is modulated to provide cooling only as required, reducing fluid consumption


  • Smooth hydraulic controls and superior balance provide market leading comfort and controllability
  • High capacity HVAC system provides dependable cooling and heating for maximum comfort
  • Improved stabilizer controls to equalize stabilizer actuation resulting in optimized uniformity of footing in varying ground conditions


  • Stabilizer movement alarm alerts bystanders of stabilizer movement
  • Pilot enable alarm alerts bystanders when pilot function is engaged
  • Ground level access of engine, fuel, pilot, and case drain filters as well as electrical service box


  • Reinforced fabricated booms with optimized cross sections designed to withstand heavy side-to-side delimbing applications and maximize lift capability
  • Field proven cooling system keeps engine and robust hydraulic system cool, extending component life
  • Larger diameter pins feature heavy-duty plating for improved durability and excluder seals to retain grease and keep free of SP contaminant


  • Single cylinder main boom has fewer parts to service than traditional dual cylinder lift system
  • Standard electric fill pump for hydraulic oil is at ground level for safe, easy service
  • Hinged doors provide industry-leading access to core components, daily check points, and service locations

Cat Work Tools

  • Optimized Cat XT™-6 ToughGuard™ hose routings on GLK Series grapple designed to minimize loosening of fittings and improve hose life
  • Larger GLK Series cylinder pins and bushings reduce bearing stress by 25 percent
  • Available now in both a TW “Tapered Wide” and SN “Straight Narrow,” the GLK Series grapple is suitable for additional applications
  • Standard hold valves on GLK Series log grapples improve log retention
  • GLK Series grapples feature optional three port swivel which allows mounting of grapple saw
  • DLK426 delimber knives now have larger diameter pins that reduce bearing stress by 12 percent

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