170-9918 CAT 385C 390D Variable Piston Pump

Product Overview

The 170-9918 is a Caterpillar Hydraulic Piston Pump listed in the official Cat Parts Store. Cat identifies the unit as a Variable Displacement Axial Piston Pump and lists 10R-3223 as the corresponding Cat Reman Hydraulic Pump.

Caterpillar’s official compatibility data includes 385B, 385C, 385C FS, 385C L, 385C L MH, 390D, 390D L and 5090B applications. The catalog also associates 385C and 385C L with mobile hydraulic power unit applications.

For heavy-duty excavator hydraulic systems, replacement quality depends on more than external fit. The pump must be matched to the machine configuration, mounting geometry, drive interface and hydraulic circuit requirements.

Our replacement engineering process focuses on interchangeability, dimensional consistency and 100% simulated operating-condition testing, with attention to rotating-group condition, leakage, hydraulic response and continuous running stability.

Part Number Identification

• CAT OEM Part Number: 170-9918
• Part Number without separator: 1709918
• Cat Reman Part Number: 10R-3223
• Product Type: Hydraulic Piston Pump
• Pump Architecture: Variable Displacement Axial Piston Pump
• Housing Material: Ductile (Spheroidal) Iron
• Official Compatible Models: 385B, 385C, 385C FS, 385C L, 385C L MH, 390D, 390D L, 5090B

Technical Specifications

• Brand: Caterpillar / CAT
• OEM Part Number: 170-9918
• Part Number without hyphens: 1709918
• Cat Reman Reference: 10R-3223
• Product Type: Hydraulic Piston Pump
• Pump Architecture: Variable Displacement Axial Piston Pump
• Housing Material: Ductile (Spheroidal) Iron
• Official Published Length: 12.1 in
• Official Published Height: 9.36 in
• Official Published Width: Not published on the current Cat Parts Store page
• Displacement: Not published on the current official Cat public page
• Rated Pressure: Not published on the current official Cat public page
• Peak Pressure: Not published on the current official Cat public page
• Maximum Speed: Not published on the current official Cat public page
• Detailed Control Configuration: Not published for this specific part number
• Weight: Not published on the current official Cat public page
• Official Compatible Models: 385B, 385C, 385C FS, 385C L, 385C L MH, 390D, 390D L, 5090B
• Cat Reman Equivalent: 10R-3223

Caterpillar officially confirms the pump architecture, ductile-iron material, published dimensions and compatible models.

Because Caterpillar’s public listing does not publish verified displacement, pressure, speed or detailed controller data for this exact part number, these values have intentionally not been filled with third-party estimates.

Key Technical Advantages

1. Variable Displacement Axial Piston Architecture

Caterpillar identifies 170-9918 as a Variable Displacement Axial Piston Pump.

The axial piston architecture uses a rotating group and swashplate mechanism to convert mechanical input into hydraulic flow. Variable displacement allows hydraulic output to adapt to changing machine demand, which is particularly relevant for large excavator work cycles.

2. Heavy-Duty Excavator Application

The official Cat catalog lists 170-9918 for several large hydraulic excavator configurations, including 385B, 385C and 390D, as well as 5090B front-shovel applications.

These machines place demanding requirements on hydraulic components because of high load cycles, frequent pressure changes, prolonged operating periods and thermal stress.

3. Ductile Iron Housing

Caterpillar specifies Ductile (Spheroidal) Iron for 170-9918.

Ductile iron provides a combination of strength and toughness suitable for heavy hydraulic-pump housings exposed to pressure pulsation, mounting loads and equipment vibration.

For replacement manufacturing, material consistency should be supported by precise machining of bearing bores, mounting surfaces, hydraulic-port locations and sealing interfaces.

4. OEM / Reman Traceability

Caterpillar officially identifies 10R-3223 as the associated Cat Reman hydraulic pump for 170-9918. The official listings also show the same published overall dimensions of 12.1 in × 9.36 in.

This provides a clear sourcing reference for maintenance and replacement procurement.

5. Defined Installation Envelope

The official published dimensions are:

• Length: 12.1 in
• Height: 9.36 in

The same dimensions are listed for 10R-3223.

These dimensions are useful for preliminary installation checks, although final compatibility must include mounting, hydraulic and drive-interface verification.

6. Precision Replacement Engineering

For a heavy-duty variable axial piston pump, replacement manufacturing should focus on:

• Cylinder-block geometry
• Piston-to-bore clearance
• Slipper geometry
• Valve-plate contact condition
• Bearing fit
• Shaft runout
• Sealing-surface quality
• Internal leakage control

These factors affect volumetric performance, heat generation, noise and long-term operating stability.

Application Areas

Caterpillar’s official parts catalog lists the following applications for 170-9918:

• Caterpillar 385B Excavator
• Caterpillar 385C Excavator
• Caterpillar 385C FS
• Caterpillar 385C L
• Caterpillar 385C L MH
• Caterpillar 390D
• Caterpillar 390D L
• Caterpillar 5090B Front Shovel
• 385C / 385C L Mobile Hydraulic Power Unit applications

These applications are based on the current Cat catalog. Specific machine compatibility should still be verified against the equipment serial number and current configuration because Caterpillar warns that configuration changes can affect actual fitment.

Expert Maintenance Tips

1. Verify the Complete Part Number

Before installation, confirm that the original unit is identified as:

170-9918

Also verify whether 10R-3223 is the correct Cat Reman reference for the actual machine configuration. Caterpillar officially associates these two references.

2. Check Installation Dimensions

The published dimensions are:

• Length: 12.1 in
• Height: 9.36 in

Before installation, confirm surrounding clearance, hose routing and mounting geometry.

3. Inspect the Drive System

Before installing the replacement pump, inspect:

• Drive shaft
• Coupling
• Shaft splines
• Shaft alignment
• Bearing condition
• Torsional-wear marks

A mechanical drive problem can damage a correctly manufactured replacement pump.

4. Remove Contamination From the Hydraulic System

If the previous pump suffered severe wear, metallic particles may remain in the hydraulic circuit.

Before commissioning the replacement unit:

• Check hydraulic oil condition.
• Inspect or replace filters.
• Clean the reservoir.
• Inspect the suction line.
• Inspect return-line condition.
• Remove visible metallic contamination.

Precision interfaces within the piston, slipper and valve-plate assemblies are particularly sensitive to abrasive contamination.

5. Commission Under Gradual Load

After installation, begin with low-load operation and monitor:

• Hydraulic oil level
• Suction condition
• Abnormal noise
• External leakage
• Pressure stability
• Oil temperature
• Vibration

Increase the operating load progressively after confirming stable initial operation.

6. Perform 100% Simulated-Condition Testing

Recommended factory testing for a 170-9918 replacement includes:

• Rotation testing
• Flow-response testing
• Pressure-response testing
• Variable-displacement response testing
• Internal and external leakage inspection
• Continuous running testing
• Thermal stability testing
• Noise and vibration inspection

Simulated-load testing provides a stronger basis for evaluating interchangeability and long-term reliability than a simple no-load functional test.

OEM Verification Reference

Primary source: Caterpillar official Parts Store listing for 170-9918 and Cat Reman listing for 10R-3223.

Caterpillar officially confirms:

• 170-9918 is a Cat Hydraulic Piston Pump.
• The architecture is identified as a Variable Displacement Axial Piston Pump.
• The housing material is Ductile (Spheroidal) Iron.
• Published dimensions are 12.1 in length × 9.36 in height.
• 10R-3223 is listed as the corresponding Cat Reman hydraulic pump.
• Compatible applications include 385B, 385C, 385C FS, 385C L, 385C L MH, 390D, 390D L and 5090B.