Understanding High Flow Hydraulic Systems on the 1998 Gehl 5635DX Skid Steer

[MikePhua]

Introduction to High Flow Hydraulic Systems
High flow hydraulic systems in skid steer loaders like the 1998 Gehl 5635DX provide increased hydraulic oil volume and pressure to power a wider range of attachments requiring more hydraulic flow, such as cold planers, stump grinders, and hydraulic breakers. Unlike standard flow systems, which supply limited hydraulic capacity sufficient for typical buckets and forks, high flow setups deliver enhanced performance for demanding tasks.
Operators often wonder whether their machine is equipped with high flow hydraulics, as this impacts attachment compatibility and machine versatility.
Identifying High Flow on the Gehl 5635DX
Several indicators can help determine if a 1998 Gehl 5635DX has a high flow hydraulic system:

• Factory Specifications: The 5635DX was offered with an optional high flow hydraulic package. Checking original equipment manuals or dealer records can confirm the presence of this option.
  
• Hydraulic Flow Rate: Standard flow rates for the Gehl 5635DX hover around 17-20 gallons per minute (GPM), while high flow systems can provide 30 GPM or more.
  
• Additional Hydraulic Ports: High flow models usually have extra hydraulic couplers or different plumbing to support auxiliary attachments.
  
• Pump Type and Size: High flow systems often use a larger displacement hydraulic pump or a variable displacement pump capable of higher output.
  
• Control Valves: Presence of specialized or additional control valves dedicated to the auxiliary circuit suggests high flow capability.
  

Why High Flow Matters
High flow hydraulic systems allow the skid steer to operate attachments that require significant hydraulic power:

• Cold Planers: Used for asphalt milling and surface preparation, needing high hydraulic volume for drum rotation.
  
• Hydraulic Breakers: Used for demolition work, demanding high impact energy driven by hydraulic pressure and flow.
  
• Stump Grinders: Require strong hydraulic flow to power the rotating cutting head efficiently.
  

Without high flow hydraulics, these attachments either perform poorly or cannot be operated safely, limiting the machine’s utility.
How to Measure Hydraulic Flow
For precise confirmation, measuring hydraulic flow is effective:

• Flow Meter: Install a hydraulic flow meter on the auxiliary circuit to record GPM output at various engine speeds.
  
• Pressure Gauge: Measuring system pressure along with flow provides a complete picture of hydraulic capability.
  
• Test Attachments: Trying known high flow attachments and observing performance also offers practical insight.
  

Potential Modifications and Upgrades
Some owners choose to retrofit or upgrade their 5635DX with aftermarket high flow kits to expand attachment options:

• Pump Replacement: Installing a higher capacity or variable displacement pump.
  
• Control Valve Upgrade: Adding valves capable of handling increased flow and pressure.
  
• Hydraulic Hose and Coupler Changes: Upgrading to components rated for higher flow rates.
  

While these upgrades increase versatility, they require professional installation and careful system tuning to avoid damage.
Terminology Explained

• GPM (Gallons Per Minute): A measure of hydraulic fluid flow rate, indicating volume delivered per minute.
  
• Auxiliary Hydraulic Circuit: The hydraulic system circuit dedicated to powering attachments beyond the machine’s primary functions.
  
• Variable Displacement Pump: A pump capable of adjusting flow output based on demand, improving efficiency.
  
• Hydraulic Couplers: Connectors allowing quick attachment or detachment of hydraulic hoses to auxiliary equipment.
  

Real-World Example: Increased Productivity with High Flow
A landscaping company upgrading from a standard flow 5635DX to a high flow variant reported significant productivity gains. The ability to run a cold planer attachment allowed them to take on asphalt repair jobs previously outsourced. This led to increased revenue streams and better equipment utilization.
Maintenance Considerations
High flow systems experience greater hydraulic fluid volume and pressure, requiring:

• More frequent hydraulic fluid and filter changes.
  
• Regular inspection of hoses and fittings for wear or leaks.
  
• Monitoring hydraulic temperatures to prevent overheating.
  
• Ensuring auxiliary controls function correctly to avoid damage.
  

Summary Checklist for Confirming High Flow on Gehl 5635DX

• Check factory option and documentation for high flow package.
  
• Inspect for additional hydraulic couplers and plumbing.
  
• Identify pump specifications and type.
  
• Measure hydraulic flow using appropriate tools.
  
• Test operation with high flow attachments if available.
  

Conclusion
Determining whether a 1998 Gehl 5635DX skid steer has a high flow hydraulic system is crucial for matching attachments and maximizing machine capability. By understanding factory specifications, inspecting physical components, and measuring hydraulic output, owners can make informed decisions about equipment use or upgrades. High flow hydraulics broaden the operational scope of skid steers, enhancing productivity in demanding applications.