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JLG 40F Boom Lift Still Delivers Reliable Elevation After Decades
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The JLG 40F and Its Industrial Origins
The JLG 40F boom lift was manufactured in the late 1970s, during a period when aerial work platforms were rapidly evolving to meet the needs of industrial maintenance and construction. JLG Industries, founded in 1969 in McConnellsburg, Pennsylvania, quickly became a leader in the aerial lift market by focusing on rugged design and operator safety. The 40F model was built for factory use, warehouse maintenance, and overhead crane servicing, offering a working height of approximately 46 feet and a platform capacity suitable for tools and personnel.
Unlike modern articulating booms with advanced electronics, the 40F relied on straightforward hydraulic controls and mechanical drive systems. Its simplicity made it a favorite in environments where reliability and ease of service were paramount.
Performance on Flat Surfaces vs Sloped Terrain
The 40F performs well on flat concrete, where its drive motors and weight distribution allow smooth movement and stable elevation. However, on sloped surfaces, the machine may struggle due to limited torque and traction. This is especially true if the drive units are worn or if the hydraulic system has aged without regular maintenance.
Factors affecting slope performance:
  • Hydraulic pump output and motor efficiency
  • Tire condition and inflation pressure
  • Weight balance and counterweight integrity
  • Drive motor torque rating and gear reduction
A technician in Ohio noted that his 40F, previously used in a factory setting, moved effortlessly on polished concrete but hesitated on a 10-degree incline. After inspecting the drive motors, he found that one unit had reduced output due to internal leakage.
Drive Unit Inspection and Troubleshooting
To restore full mobility, the drive units should be inspected for:
  • Hydraulic fluid contamination
  • Seal integrity and leakage
  • Motor shaft play or binding
  • Electrical solenoid function (if equipped)
  • Hose routing and pressure loss
Recommended steps:
  • Drain and replace hydraulic fluid with ISO 46 or ISO 68 grade
  • Clean or replace filters
  • Test motor output under load
  • Check for heat buildup during operation
  • Replace worn tires with industrial-grade non-marking rubber
A restorer in Illinois rebuilt his 40F’s drive motors using aftermarket seals and reported improved slope handling and reduced noise.
Tow Bar Use and Emergency Mobility
The 40F includes a tow bar for emergency relocation. While not intended for regular transport, the tow bar allows the machine to be moved short distances if the drive system fails. Operators should ensure:
  • Tow bar is securely attached to designated mounting points
  • Machine is on level ground
  • Personnel are clear of the boom and platform
  • Hydraulic brakes are disengaged or bypassed
A crew in Michigan used the tow bar to reposition a disabled 40F during a power outage. The process took under 10 minutes and avoided the need for a forklift or crane.
Manuals and Parts Breakdown Are Essential
Having access to the original operator’s manual and parts breakdown is invaluable for servicing legacy equipment. These documents provide:
  • Hydraulic schematics
  • Wiring diagrams
  • Torque specifications
  • Component part numbers
  • Safety procedures and inspection intervals
Operators should store manuals in waterproof containers inside the machine or digitize them for mobile access. Annotating pages with service history and replacement part sources can streamline future repairs.
Preserving and Operating Vintage Boom Lifts
To keep older machines like the 40F in service:
  • Perform monthly hydraulic system checks
  • Lubricate pivot points and cylinder pins
  • Inspect welds and structural components annually
  • Replace control switches and wiring as needed
  • Upgrade lighting and safety decals to meet current standards
A facility manager in Ontario implemented a preventive maintenance schedule for his 1978 40F and extended its operational life by over a decade.
Conclusion
The JLG 40F boom lift, though built nearly half a century ago, remains a capable and dependable machine when properly maintained. Its mechanical simplicity, factory-grade durability, and straightforward controls make it ideal for indoor maintenance and light-duty elevation tasks. With attention to drive units, hydraulic health, and documentation, the 40F continues to prove that old iron still has a place in modern operations. In aerial access, reliability often outlasts innovation—and the 40F is living proof.
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