Locating the Transmission Oil Pump on a Ford 555 Backhoe

[MikePhua]

The transmission oil pump—often called the “charge” pump—is mounted directly on the input shaft of the transmission, meaning it's driven by the main shaft that transmits engine torque into the gearbox system . In practical terms, this places the pump deep inside the transmission housing, forming a bridge between the engine output and transmission internals.

Why Location Matters

• Being on the input shaft ensures the pump begins pressurizing transmission fluid as soon as the engine turns over.
  
• This pressurized oil supports the torque converter, shifts gears smoothly, and supplies vital lubrication throughout the power train.
  

Pump Specifications and Fitment

• The commonly used replacement pump carries part number 86516596, compatible with models such as Ford 555, 555A, 555B, and others in the series .
  
• It's a compact, 9-lb unit designed to withstand continuous rotation and hydraulic pressure inside the transmission housing .
  

Service Challenges & Considerations
Once disassembled, the pump’s proximity to the torque converter and transmission internals means:

• Access is difficult — removing the transmission housing or bell housing is typically required for repair or replacement.
  
• Contamination risk — always clean the surrounding area to prevent debris from entering the system when opening it.
  
• The suction tube inside the pump assembly often contains a mesh filter, necessary to trap particles. Careful reinstallation is critical to ensure reliable fluid intake.
  

Practical Suggestions

• Plan for teardown: Expect to split or partially remove the transmission to access the pump and suction mesh.
  
• Clean thoroughly: Before any disassembly, wipe the housing and immediate surroundings to avoid introducing contaminants.
  
• Inspect related parts: Always check the torque converter mounting and input shaft seals—damage there can disrupt pump performance.
  
• Use OEM or equivalent parts: Opt for proven pump part numbers (e.g., 86516596) for durability.
  
• Test before reassembling fully: Turn the engine with components reinstalled to ensure fluid flow and pressure before final closure.
  

Terminology Cheat Sheet

• Charge Pump / Transmission Oil Pump: Drives hydraulic pressure required for gear shifts and torque converter lubrication.
  
• Input Shaft: The transmission’s main shaft that receives engine power and runs the pump.
  
• Mesh Suction Filter: Screen within the suction tube that filters debris from entering the pump.
  
• Torque Converter: Hydraulic coupling between engine and transmission that multiplies torque and allows for smooth shifts.
  
• Bell Housing: The protective casing bridging engine and transmission, typically removed to access internal components.
  

A Maintenance Anecdote
Imagine a rural road crew working miles from the nearest parts supplier. Their trusty Ford 555 backhoe begins losing drive power—hydraulic pressure isn’t making it through. After splitting the transmission, they find the pump’s mesh screen clogged with grit from a neglected cable entry point. A quick clean and replacement of the charge pump restores full torque converter pressure. The backhoe roars back to life—showing how critical both understanding and upkeep of this hidden component truly are.

Brief Chapter: Ford 555 Backhoe & Manufacturer Insight
These backhoe loaders emerged in the 1970s and 1980s as rugged, versatile machines suited for both agricultural and construction use. Built under the Ford/New Holland banner, the 555 series featured hydraulic drivetrain systems with torque converters—highlighting the importance of transmission oil pumps in smooth operation.
Globally, thousands of units were sold, popular among rental fleets and small contractors for their reliability and serviceability. Ford, known since the 1920s for durable tractors, leveraged decades of industrial machinery experience. Over time, their backhoes evolved to integrate better hydraulics and ergonomics, becoming trusted tools worldwide.

Summary Overview

• Location: Mounted on the transmission input shaft.
  
• Access: Requires significant disassembly—bell housing or housing removal.
  
• Key Components:
  • Charge pump part number 86516596 (common replacement).
    
  • Mesh suction filter within pump assembly.
    
• Best Practices:
  • Keep clean before opening.
    
  • Inspect seals, torque converter condition.
    
  • Reinstall with OEM-equivalent parts.
    
• Impact of Failure: Without pump output, the torque converter starves, leading to shifting loss or drive failure.
  

Understanding the pump's hidden location and maintaining its integrity can prevent transmission failures and keep your Ford 555 performing reliably—year after year.