Who Manufactured the Loader Valve on the Mid-1970s IH 3500A

[MikePhua]

The IH 3500A and Its Hydraulic Legacy
The International Harvester 3500A was a robust industrial tractor-loader produced during the mid-1970s, designed for heavy-duty applications in construction, agriculture, and municipal work. Built on the same platform as IH’s agricultural tractors but reinforced for loader use, the 3500A featured a front-end loader powered by a dedicated hydraulic system. Its popularity stemmed from its mechanical simplicity and the widespread availability of parts through IH’s extensive dealer network at the time.
International Harvester, founded in 1902, was a dominant force in agricultural and industrial machinery until its merger with J.I. Case in 1985. The 3500A was part of a generation of machines that emphasized modular design, allowing components like hydraulic valves and loader assemblies to be serviced or replaced independently.
Hydraulic Valve Identification and Configuration
The loader valve on the IH 3500A appears to resemble the V30 series stack valve, a modular hydraulic valve system commonly used in industrial equipment during the 1970s. These valves were manufactured by companies like Cross Manufacturing, Parker Hannifin, and Gresen Hydraulic. The V30 series is known for its stackable design, allowing multiple valve sections to be combined for different functions.
Key characteristics of the V30 series include:

• Bolt patterns with external lower bolts, not centered between fluid passages
  
• Modular sections for lift, tilt, and auxiliary functions
  
• Compatibility with open-center and closed-center hydraulic systems
  

The IH 3500A was often equipped with a two-section valve for bucket lift and tilt, with an optional third section for auxiliary functions like a side-shifter or grapple.
Terminology Explained

• Stack Valve: A hydraulic valve composed of multiple sections bolted together to control different functions.
  
• Auxiliary Valve: An additional valve section used to power attachments beyond the standard loader functions.
  
• Open-Center System: A hydraulic system where fluid flows continuously until a valve is activated.
  

Adding an Auxiliary Function
Owners seeking to add a forklift side-shifter or other hydraulic attachment to the IH 3500A can do so by sourcing a compatible valve section. If the original valve is a V30 series, a matching auxiliary section can be added to the stack. However, sourcing vintage valve sections can be challenging due to obsolescence.
Recommendations include:

• Inspect the valve body for manufacturer markings or serial numbers
  
• Compare bolt patterns and fluid port locations to V30 schematics
  
• Contact hydraulic suppliers who specialize in vintage or legacy systems
  
• Consider replacing the entire valve stack with a modern equivalent if compatibility is uncertain
  

A Story from the Field
In Pennsylvania, a restorer working on a 1975 IH 3500A wanted to add a hydraulic side-shifter to his loader. The dash already had a cutout and labeled pivot point for an auxiliary lever, suggesting the tractor was prepped for expansion. After comparing the valve to a V30 schematic, he confirmed the bolt pattern matched. He sourced a used V30 auxiliary section from a salvage yard and installed it successfully, restoring full functionality to the loader.
Preventive Maintenance Tips

• Replace hydraulic fluid every 500 hours
  
• Inspect valve seals annually for leaks or wear
  
• Clean valve spools and check for scoring during service
  
• Use compatible hydraulic oil with anti-foaming additives
  

Conclusion
The mid-1970s IH 3500A loader likely used a V30 series stack valve or a similar modular hydraulic valve system. While identifying the exact manufacturer may require inspection of markings or bolt patterns, the design lends itself to expansion and repair. With careful sourcing and mechanical diligence, owners can restore or upgrade the hydraulic system to meet modern needs.