Correcting Reversed Hydraulic Controls on a Case 1840 Skid Steer

[MikePhua]

The Case 1840 and Its Hydraulic Drive System
The Case 1840 skid steer loader, produced from the early 1990s through the early 2000s, remains one of the most widely used compact machines in North America. With over 60,000 units sold, its reputation for mechanical simplicity and reliability has made it a favorite among contractors, farmers, and rental fleets. Powered by a 51-horsepower Cummins 4B diesel engine and equipped with a chain-driven hydrostatic transmission, the 1840 uses dual hydraulic pumps to control left and right drive motors independently.
Each joystick in the operator’s cab is linked to a hydraulic control valve that directs fluid to the drive motors. Forward and reverse movement is achieved by varying the flow direction through these valves. The system is simple, but it depends entirely on correct hose routing. If hoses are misconnected, the machine may behave erratically—such as reversing when the joystick is pushed forward.
Symptoms of Reversed Hose Connections
After replacing several damaged hydraulic hoses using the factory diagram, one operator noticed that the right joystick behaved normally, but the left joystick was inverted. Pushing forward caused the machine to reverse on the left side, and pulling back caused it to move forward. This is a classic sign of reversed hydraulic flow due to incorrect hose routing.
Common symptoms include:

• Asymmetric movement when turning
  
• One side of the machine responding opposite to joystick input
  
• No fault codes or warning lights
  
• No visible leaks or pressure loss
  

Terminology:

• Hydrostatic drive: A propulsion system using hydraulic fluid to power wheel motors
  
• Drive motor: A hydraulic motor mounted to each side of the loader, converting fluid pressure into rotational motion
  
• Control valve: A directional valve that regulates fluid flow based on joystick input
  

Identifying and Correcting Hose Routing
The Case 1840 uses four primary hoses to control the left and right drive motors—typically labeled A, B, C, and D in service diagrams. In this configuration:

• Hoses A and B control the right motor
  
• Hoses C and D control the left motor
  

If the right side operates correctly, hoses A and B are likely installed properly. The issue lies with hoses C and D. Reversing these two hoses will correct the flow direction and restore proper joystick behavior.
Steps to correct:

• Identify hoses C and D at either the pump or motor end
  
• Swap their connections at one end only (either pump or motor, not both)
  
• Ensure fittings are clean and torqued to spec
  
• Test joystick input and observe machine response
  

Important note: Swapping hoses at both ends will cancel the correction and preserve the reversed behavior. Only one end should be changed.
Field Anecdote and Practical Insight
In a similar case, a technician in Texas replaced all hydraulic hoses on a Case 1840 using a diagram but noticed the left side was behaving in reverse. After confirming the right side was correct, he swapped hoses C and D at the motor end. The machine immediately responded correctly, and the issue was resolved without further disassembly.
This highlights the importance of understanding directional flow in hydrostatic systems. Even with accurate diagrams, hose labeling and routing can be misinterpreted—especially when fittings are similar in size and location.
Preventative Measures and Hose Replacement Tips
To avoid future routing errors:

• Label hoses with colored zip ties or tags before removal
  
• Photograph hose layout prior to disassembly
  
• Use OEM diagrams and verify orientation from the operator’s seat
  
• Replace hoses with pressure-rated equivalents (typically 3,000 psi minimum)
  
• Inspect fittings for wear and replace O-rings during reinstallation
  

Hydraulic hose replacement is a common maintenance task, but small errors can lead to major control issues. Taking time to document and verify connections ensures safe and predictable operation.
Conclusion
Reversed hydraulic controls on a Case 1840 skid steer are almost always caused by misrouted hoses—specifically the pair controlling the affected drive motor. By identifying and swapping hoses C and D at one end, technicians can restore proper joystick behavior and eliminate directional confusion. In hydrostatic systems, fluid flow is everything—and when it flows the wrong way, the machine will tell you. All you have to do is listen, and know which hose to move.