350-0666 Cat Hydraulic Piston Pump

Product Overview

The 350-0666 Cat Hydraulic Piston Pump is a hydraulic pump used on selected Caterpillar backhoe loader configurations.

According to the official Cat Parts Store, 350-0666 is identified as a Hydraulic Piston Pump and is classified as a Variable Displacement Axial Piston Pump. Cat officially lists the 414E, 416E, 422E, 428E and 434E backhoe loaders as compatible models.

Cat also publishes a material specification of Carbon Steel and overall dimensions of approximately 12.6 in length × 6.7 in height for this part number. Cat lists 20R-4693 Cat Reman Piston Pump among the relevant alternative parts.

For aftermarket replacement applications, true interchangeability must be verified against the original pump configuration, including mounting interface, shaft, ports, rotation and control arrangement.

Our replacement program is focused on form-fit-function replacement, controlled precision machining and 100% simulated working-condition testing.

This aftermarket product should not be represented as a Caterpillar OEM-authorized or Caterpillar-manufactured product unless such authorization exists.

Technical Specifications

• Part Number: 350-0666
• Brand Reference: Caterpillar / Cat
• Pump Type: Hydraulic Piston Pump
• Pump Architecture: Variable Displacement Axial Piston Pump
• Equipment Type: Backhoe Loader
• Officially Listed Compatible Models:
  • Cat 414E
  • Cat 416E
  • Cat 422E
  • Cat 428E
  • Cat 434E
• Length: 12.6 in / approximately 320 mm
• Height: 6.7 in / approximately 170 mm
• Material: Carbon Steel
• Displacement: Not published on the current official Cat product page reviewed
• Rated Pressure: Not published on the current official Cat product page reviewed
• Peak Pressure: Not published on the current official Cat product page reviewed
• Maximum Speed: Not published on the current official Cat product page reviewed
• Control Configuration: Variable displacement is confirmed; the complete regulator/compensator code is not published on the current public Cat page
• Weight: Not published on the current official Cat product page reviewed
• Related Cat Reman Part: 20R-4693
• Factory Fit: Cat identifies the part as designed to fit equipment according to manufacturer specifications, while warning that machine configuration changes may affect compatibility.

Key Technical Advantages

1. Variable Displacement Axial Piston Design

The 350-0666 uses a variable-displacement axial piston architecture. This allows hydraulic output to be matched to changing system demand more effectively than a basic fixed-displacement pump.

Backhoe loaders operate with rapidly changing hydraulic requirements between loader functions, backhoe functions, steering and auxiliary circuits. A variable-displacement architecture is therefore well suited to this type of mobile hydraulic application.

2. Precision Internal Clearances

Axial piston pump efficiency depends heavily on the quality and consistency of internal running clearances.

Critical manufacturing areas include:

• Cylinder block geometry
• Piston and bore clearance
• Valve plate flatness
• Rotating-group alignment
• Bearing seating
• Sealing surfaces

Control of these parameters directly affects volumetric efficiency, heat generation, leakage and service life.

3. Carbon Steel Construction

Cat’s public specification identifies the 350-0666 material as Carbon Steel.

For heavy mobile hydraulic applications, material stability and dimensional consistency are important because the housing must withstand mechanical loading, mounting forces and hydraulic pressure loads.

4. Application-Specific Fit

Cat lists the 350-0666 for the 414E, 416E, 422E, 428E and 434E backhoe loaders and warns that equipment configuration changes can affect part fit.

A professional replacement assessment should therefore verify:

• Mounting interface
• Drive shaft
• Port arrangement
• Rotation
• Control configuration
• Hydraulic circuit configuration

5. 100% Simulated Working-Condition Testing

Our manufacturing process can include full functional testing under simulated operating conditions.

Recommended verification includes:

• Flow output
• Pressure response
• Internal leakage
• Rotation
• Noise and vibration
• Oil temperature
• Load simulation
• Functional endurance

This approach helps identify deviations before the pump reaches the field.

Application Areas

Cat officially lists the following equipment for 350-0666:​

• Cat 414E Backhoe Loader
• Cat 416E Backhoe Loader
• Cat 422E Backhoe Loader
• Cat 428E Backhoe Loader
• Cat 434E Backhoe Loader

Typical applications include:

• Loader hydraulic systems
• Backhoe hydraulic systems
• Boom and bucket circuits
• Stabilizer systems
• Steering-related hydraulic functions
• Auxiliary hydraulic attachments

Important Cross-Reference Clarification

The original product title also contains 296-6714 and 307-3063.

These should not automatically be presented as identical specifications.

Cat officially identifies 296-6714 as PUMP GP-PS-B, currently discontinued, with compatibility for 414E, 416E, 422E and 428E.

Cat identifies 307-3063 as a Flow Compensator Piston Pump / Variable Displacement Axial Piston Pump, with compatibility including 416E, 434F, 428F, 422F, 426 and 426 F2 configurations.

Therefore, these part numbers should preferably be handled as separate product records or verified cross-reference numbers rather than presented as one universally interchangeable pump.

Expert Maintenance Tips

1. Verify the Complete Pump Configuration

Before installation, confirm:

• Complete part number
• Machine model
• Machine serial number
• Pump nameplate
• Rotation
• Shaft configuration
• Port arrangement
• Control configuration

2. Flush the Hydraulic System After Major Pump Failure

When replacing a failed hydraulic pump, inspect the reservoir, suction line, filtration system, valves, cooler and hoses for metallic contamination.

Installing a new pump into a contaminated hydraulic circuit can cause premature failure.

3. Protect the Pump Inlet

Restricted suction lines, clogged strainers, air leaks or incorrect hydraulic-fluid viscosity can degrade inlet conditions and increase the risk of cavitation, vibration and abnormal noise.

4. Prime the Pump Correctly

Before initial operation, follow the machine manufacturer’s service procedure for filling and priming the replacement pump. Avoid extended operation without adequate oil supply.

5. Record Baseline Performance

Whenever possible, record system pressure, oil temperature, actuator response and pump noise before removing the old pump. Repeat the same measurements after installation to verify the repair.