Restoring Hydraulic Control on a JLG 40F Man Lift with Racine Valves

[MikePhua]

The JLG 40F and Its Role in High-Reach Access Equipment
The JLG 40F is a legacy model in the aerial work platform category, designed for high-reach applications in construction, maintenance, and demolition. Manufactured by JLG Industries, a company founded in 1969 and now a global leader in access equipment, the 40F was part of a generation of lifts that emphasized mechanical simplicity and robust hydraulic control. With a working height of approximately 46 feet and a platform capacity exceeding 500 lbs, the 40F was widely used across North America in the 1980s and early 1990s.
JLG’s early models often featured Racine hydraulic valve banks—modular, stackable units with electric-over-hydraulic actuation. These valves were known for their reliability but have become increasingly difficult to source as production ceased and newer models transitioned to Vickers or Parker systems.
Identifying the Servo Section Failure
In one restoration project, a fully refurbished JLG 40F exhibited a critical failure in its hydraulic control system. A cracked electric valve within a three-section Racine valve bank began spraying hydraulic fluid when activated. The damaged component was identified as a servo section—also referred to as a pilot or proportional control module—responsible for modulating flow based on electrical input.
Key identifiers included:

• Racine tag number: 97 986204 90
  
• Cast part number on valve: 253348-5
  
• Updated part number from JLG schematic: 7004817
  
• Bare casting part number: 253443
  
• Full servo section assembly: Racine 708150
  

The servo section’s failure rendered the lift inoperable, and sourcing a replacement proved challenging due to discontinued production and limited aftermarket availability.
Repair Options and Retrofit Strategies
Faced with the unavailability of direct replacements, technicians explored several alternatives:

• Fabricating a new servo body from 4140 steel at a precision machine shop
  
• Replacing the entire valve bank with a modern equivalent from Vickers or Parker
  
• Salvaging compatible parts from other JLG models such as the 60H, 70H, 80HX, and 86HX
  
• Purchasing a used valve bank and transplanting functional sections
  

Each option carried trade-offs in cost, compatibility, and deviation from factory specifications. Fabrication required high-precision machining and knowledge of hydraulic tolerances. Retrofitting a new valve bank involved reconfiguring wiring, mounting brackets, and flow paths—potentially compromising the lift’s original design.
Legacy Valve Systems and Intrinsically Safe Actuation
The Racine valves used in the 40F were designed with intrinsically safe electrical-over-pilot actuation. This means the electrical signal triggered a pilot pressure that moved the main spool, allowing for fine control and reduced risk of electrical hazards in volatile environments. These systems were common in early aerial lifts and industrial machinery but have since been replaced by fully proportional electrohydraulic valves with integrated diagnostics.
Understanding the terminology:

• Servo section: The pilot-controlled module that regulates main spool movement
  
• Spool section: The core valve that directs hydraulic flow to actuators
  
• Dump valve: A safety feature that releases pressure in emergency situations
  

Maintaining compatibility with these legacy systems requires careful attention to voltage ratings, connector types, and hydraulic flow characteristics.
A Story from the Field
In Oregon, a technician restoring a JLG 40F for a local contractor faced mounting pressure to complete the job. After contacting over 60 suppliers and salvage yards, he discovered that early H-series JLG lifts also used Racine valves. However, by 1984, JLG had transitioned to Vickers systems, narrowing the pool of compatible donors.
Eventually, he located a schematic identifying the servo section as item #51 and confirmed the part number as 7004817. Though the part was out of stock nationwide, a retired mechanic in Alberta offered guidance and confirmed the valve’s lineage. The technician then explored machining a replacement body, coordinating with a regional shop capable of replicating the casting and internal geometry.
The lift was saved from scrapping, and the restoration was completed with a mix of original and remanufactured components.
Recommendations for Legacy Equipment Owners
To manage aging hydraulic systems:

• Document all valve part numbers and casting codes during teardown
  
• Maintain a database of compatible models and donor machines
  
• Build relationships with machine shops capable of precision hydraulic work
  
• Consider stocking spare valve sections for future repairs
  
• Avoid mixing valve brands unless flow and control logic are fully understood
  

For rare components like Racine servo sections, proactive sourcing and preservation are essential. Once a part fails, the window for repair narrows quickly.
Conclusion
Restoring hydraulic control on a JLG 40F man lift with Racine valves is a testament to persistence, technical knowledge, and creative problem-solving. As legacy machines age, their value lies not just in their steel and hydraulics—but in the stories of those who keep them alive. Whether through machining, retrofitting, or scavenging, each successful repair extends the life of equipment that once shaped skylines and built infrastructure. In the world of high-reach lifts, every valve tells a story—and every fix is a triumph over obsolescence.