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


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

Operating Specifications

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

Service Refill Capacities

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

Hydraulic System

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


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


OFPS OFPS cab meets SAE J2267 OFPS cab meets SAE J2267 Less

Shipping Dimensions - Mounted Trailer

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

GLK Series Grapples - GLK48

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

GLK Series Grapples - GLK55

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


  • 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