Filtration Procedure for Off-Highway Truck (769-777) Rear Axle Oil {0680, 0768, 3260, 4050} Caterpillar

Filtration Procedure for Off-Highway Truck (769-777) Rear Axle Oil {0680, 0768, 3260, 4050}


769C 01X

Off-Highway Truck/Tractor
69D (S/N: 9SS1-UP; 9XS1-UP)
73D (S/N: 9YS1-UP)
769 (S/N: 99F1-UP; 35W1-UP)
769B (S/N: 99F1-UP)
769C (S/N: 01X1-UP)
769D (S/N: BBB1-UP; 5TR1-UP; 5SS1-UP)
770G (S/N: KDH1-UP; ECM1-UP; ECX1-UP)
772G (S/N: LTS1-UP; KEX1-UP; LTX1-UP)
773 (S/N: 63G1-UP)
773B (S/N: 63W1-UP)
773D (S/N: NBJ1-UP; 7ER1-UP; 7CS1-UP)
773E (S/N: BDA1-UP; PRB1-UP; KEG1-UP; DJS1-UP)
773F (S/N: EED1-UP)
776D (S/N: AFS1-UP)
777 (S/N: 84A1-UP)
777B (S/N: 4YC1-UP)
777C (S/N: 4XJ1-UP)
777D (S/N: AGC1-UP; FKR1-UP; 3PR1-UP; 2YW1-UP; AGY1-UP)
777E (S/N: KDP1-UP)
777F (S/N: JRP1-UP)
777G (S/N: GT71-UP; TNM1-UP; RDR1-UP)
785D (S/N: MSY1-UP)
Quarry Truck
771C (S/N: 3BJ1-UP)
771D (S/N: BCA1-UP; 6JR1-UP; 6YS1-UP)
773G (S/N: MWH1-UP; JWS1-UP)
775B (S/N: 7XJ1-UP)
775D (S/N: 6KR1-UP; 8AS1-UP)
775E (S/N: BEC1-UP)
775F (S/N: DLS1-UP)
775G (S/N: RFM1-UP; MJS1-UP)


Table 1
Revision  Summary of Revisions for SEBF8454 
12  Added new serial number prefixes for New Product Introduction (NPI).
Removed old Point of Contacts.
New Point of Contact added to the document.
Updated copyright date to 2016. 
11  Added new serial number prefixes for New Product Introduction (NPI).
Updated copyright date to 2015. 
10  Added new serial number prefixes for New Product Introduction. 
09  Added new serial number prefixes for New Product Introduction.
Insert new copyright date.
Added Caterpillar confidential yellow statement to document.
Added PEGJ0047 "Obtaining an Oil sample for S·O·S Analysis" to references table. 
08  Added new serial number prefixes for New Product Introduction.
Added 3B-6555 Elbow to tooling table.
Added footnotes to the tooling table.
Updated photos throughout the document.
Added "Think Safety" graphic under Important Safety Information section. 

© 2016 Caterpillar All Rights Reserved. This guideline is for the use of Cat dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law. Information contained in this document is considered Caterpillar: Confidential Yellow.

This guideline enables dealers and customers to benefit from cost reductions which were made possible through an established Contamination Control Program. Fluids that are used in Caterpillar machines are highly effective unless the fluid contains damaging amounts of contaminates. Therefore, every effort must be made to reduce the contamination level within Caterpillar fluid systems. Caterpillar makes ongoing changes and improvements to the Caterpillar products. This guideline must be used with the latest technical information available from Caterpillar to ensure that such changes and improvements are incorporated when applicable.

For technical questions when using this document, work with your Dealer Technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) Interface..

If a Contamination Control Guideline is required, but not available in SIS Web, submit a feedback form in the Service Information System website.

Canceled Part Numbers and Replaced Part Numbers

This document may include canceled part numbers and replaced part numbers. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.


The instructions that are given in this guideline will enable dealers and customers to properly filter Off-Highway Truck axle oil. This procedure will reduce contamination in the oil to an acceptable ISO contamination level. This procedure may be modified by the technician for use on some machines.


If the vehicle is being serviced due to a catastrophic failure, a complete system cleaning operation is required before initializing this kidney loop filtration procedure. If the failure is not addressed early, particles from the failed component will contaminate other system components such as valves, pumps, motors, and controls. Additional component exchange and lines flushing will be required to remove most contaminates generated from the failure. The vehicle system cleaning MUST be performed prior to the kidney looping. This filtration procedure and subsequent particle count testing should be performed as a final step in the repair process.

Important Safety Information

Illustration 1g02139237

Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly.

Improper operation, lubrication, maintenance, or repair of this product is dangerous. Improper methods could result in injury or death.

Do not operate or perform any lubrication, maintenance, or repair of this product, until you understand the operation, lubrication, maintenance, and repair information. Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons.

Hazards are identified by a safety alert symbol. Safety alert symbols are followed by a signal word such as "Warning" that is shown below.

Illustration 2g01032906

The following is the meaning of this safety alert symbol:

  • Pay Attention!

  • Become Alert!

  • Your Safety is Involved.

The message that appears under the warning explains the hazard. The message will be written or pictorially shown.

Operations that may cause product damage are identified by "NOTICE" labels on the product and in this publication.

Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. Therefore, the warnings in this publication and on the product are not all inclusive. If a tool, a procedure, a work method, or an operating technique that is not recommended by Caterpillar is used, ensure that the procedure is safe for all personnel around the machine. Also ensure that the product will not be damaged or be made unsafe by the operation, lubrication, maintenance, or repair procedures.

All of the information, specifications, and illustrations that are in this publication are based on information that was available at the time of publication. The following information could change at any time: specifications, torque, pressures, measurement, adjustments, illustrations and other items. These changes can affect the service that is given to the product. Obtain the most current and complete information before starting any job. Caterpillar dealers have the most current information that is available.


------ WARNING! ------

Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine.

To prevent possible injury, perform the procedure that follows before testing and adjusting the steering system.

------ WARNING! ------

Personal injury can result from hydraulic oil pressure and hot oil.

Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system.

Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.


Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.

Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.

Dispose of all fluids according to local regulations and mandates.


Table 2
Media Number  Title 
NEHS0799  "Tool Operating Manual for 170-8500 Analyzer Group" 
NEHS0809  "Tool Operating Manual for 246-1157 Rear Axle Filter Cart" 
NENG2500  "Dealer Service Tool Catalog" 
PEGJ0045  "Reporting Particle Count by ISO Code" 
PEGJ0047  "How to take a good S·O·S sample" 
SEBF8482  "Obtaining an Oil Sample for S·O·S Analysis" 

Tooling and Equipment

Table 3
Required Tools 
Part Number  Part Description 
246-1157  Rear Axle Filter Cart 
5P-0306  Transducer 
190-9937  Final Drive Adapter(1) 
190-9940  Differential Adapter(2) 
175-3623(3)  NPT Pipe Nipple 
141-2502(3)  Bushing Reducer 
190-8322(3)  Nipple - Quick Disconnect 
169-8373  Bottle Group 
3B-6555(4)  90° Elbow (1) 
Optional Tools 
170-8500  Analyzer Gp 
210-5530  Coupler 
188-0639  Hose 
(1) Two adapters will be needed for the procedure.
(2) Only one adapter will be needed for the procedure.
(3) For the 777F Differential Adapter Only.
(4) Install the 3B-6555 Elbow on to the filter cart return hose, then attach the quick disconnect coupler to the elbow. Refer to Illustration 6, call out A for installation location of the elbow.

Off-Highway Truck Rear Axle Oil Filter Cart Procedure

The following procedure is intended for the 769 through 777 Off-Highway Truck models. The procedure is most effective when performed immediately after the axle oil has been warmed to 50 °C (122 °F) and mixed from operation. Warming the oil allows any contamination in the system oil to be placed in suspension and lowers the viscosity. Be sure to read and understand the Tool Operating Manual, NEHS0809, "246-1157 Rear Axle Filter Cart" before beginning the procedure.


Be sure to keep all parts clean and free of contamination.

  1. Park the machine on level ground. Engage the parking brake.

    Illustration 3g01285430
    (1) Air breather

  2. Remove the air breather (1) that is located on top of the rear axle housing. Refer to Illustration 3.

    Illustration 4g01285433
    (2) 5P-0306 Transducer
    (3) Air supply hose

  3. Install the Transducer (2) in place of the air breather (1) on top of the rear axle housing. Refer to Illustration 4.

  4. Operate the vacuum transducer before removing the final drive plugs and before removing the rear axle differential housing drain plug.

    Note: Be sure that the rear axle oil system has pulled a vacuum.

    Illustration 5g01285434
    (4) Final drive magnetic plug

  5. Remove one final drive magnetic plug (4). Refer to Illustration 5.

    Illustration 6g01285435
    (5) 190-9937 Final Dive Adapter

  6. Quickly install the Final Drive Adapter (5). Inspect the magnetic plug for contaminants. Refer to Illustration 6.

  7. Repeat Steps 4 through 6 for the opposite final drive.

    Illustration 7g01285437
    (6) Filter cart return hoses
    (7) Final drive valve

    Illustration 8g03494135
    (6) Filter cart return hoses
    (7) Final drive valve
    (A) Installation location of the 3B-6555 Elbow

    Note: Installation of the 3B-6555 Elbow will aid in orientation, reduce the length of return hose needed and will also reduce wear on the return hose.

  8. Connect the filter cart return hoses (6) to the left and right final drive adapters. Be sure that the final drive valves (7) are in the CLOSED position. Refer to Illustration 7.

    Illustration 9g01285438
    (8) 190-9942 Differential Adapter

  9. Remove the differential case drain plug and quickly install the Differential Adapter (8). Refer to Illustration 9.

    Note: The 777F differential requires the use of a 175-3623 NPT Pipe Nipple, 141-2502 Bushing Reducer, and a 190-3222 Quick Disconnect Nipple to connect the suction hose to the 777F differential case drain.

    Illustration 10g03492257
    (8) 190-9942 Differential Adapter
    (9) Filter cart suction hose
    (10) Differential valve

  10. Attach the filter cart suction hose (9) to the differential adapter (8). Refer to Illustration 10.

  11. Disconnect the transducer air supply to relieve the rear axle housing vacuum.

    Note: Leave the transducer connected to the rear axle to complete the filter cart removal procedure.

  12. Open both final drive valves (7). Open the differential valve (10). Refer to Illustration 7 and Illustration 10.

  13. Ensure that there are no oil leaks from any of the filter cart connections.

    Note: This filter cart connection configuration will flush contaminants toward the center differential housing and away from the final drive bearings. The filter cart will easily remove any contaminants from the lower differential housing.

    Illustration 11g03492496
    (11) Air supply hose
    (12) Air supply valve

  14. Attach an air supply hose (11) to the 246-1157 Filter Cart. Ensure that the air supply valve (12) is in the CLOSED position. Be sure that the air supply does not exceed 690 kPa (100 psi). Refer to Illustration 11.

    Illustration 12g01285444
    (12) Air supply valve

  15. Slowly open the air supply valve (12) to start the filter cart pump operation. The air pump is a double acting diaphragm pump. The pump is rated to pump 50W to 60W oil at approximately 114 L/min (30 US gpm) to 133 L/min (35 US gpm). Refer to Illustration 12.

  16. While operating the filter cart, check the filter element indicators on the filter cart. The indicators will determine the amount of capacity left in the filter element.

    Note: Occasionally, the filter cart pump will cavitate during start-up. Cavitation is due to air in the suction lines of the pump. If the cavitation continues for more than 1 minute, shut the filter cart off and check the connections.

  17. Ensure that there are no oil leaks from any of the filter cart connections.

    Note: Caterpillar recommends taking a particle count on the oil at the beginning of the filter cycle to use as a baseline particle count.

  18. The oil can be particle count tested for cleanliness in one of the two following ways.

    • Use a 170-8500 Analyzer Gp for immediate results.

    • Collect a bottle sample and send the sample to an S·O·S lab.

  19. Read Tool Operating Manual, NEHS0799, "170-8500 Analyzer Group" before operating the particle analyzer.

    Illustration 13g03492540
    (13) S·O·S valve
    (14) Fabricated suction tube
    (15) 210-5530 Coupler

  20. When using the 170-8500 Analyzer Gp, connect the "low pressure in" port to the S·O·S valve (13) on the filter cart. Refer to Illustration 13.

  21. Attach the opposite end of the fabricated suction tube to the "low pressure in" port on the portable particle counter as called for in the Tool Operating Manual.

    Illustration 14g03320131
    (13) S·O·S valve
    (16) 169-8373 Bottle Group

  22. If collecting a bottle sample, use the same S·O·S valve (13) and a 169-8373 Bottle Group (16). Refer to Illustration 14.

  23. Record an oil sample reading from the S·O·S valve (13) on the filter cart at the beginning of the filter cycle.

    Illustration 15g01285448
    (17) 246-1157 Filter Cart

  24. Operate the filter cart (17) until the portable particle analyzer indicates that the oil has reached an acceptable ISO level of at least 16/13. The final ISO level should be recorded before the machine is returned to the field.

    Note: Refer to "Oil Compartment Times for 188-3242 Filter Cart and 246-1157 Filter Cart", located at the end of this document, when a 170-8500 Analyzer Gp is not available.

  25. When the target ISO level or the time interval has been met, close the air supply valve (12). Disconnect the air supply hose (11). Refer to Illustration 11.

    ------ WARNING! ------

    Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact the skin.

  26. Close both final drive valves (7) and close the differential valve (10). Refer to Illustration 7 and Illustration 10.

  27. Disconnect all filter cart oil hoses from the Off-Highway Truck.

    Illustration 16g03493836
    (2) 5P-0306 Transducer
    (3) Air supply hose

  28. Reinstall the air supply hose (3) to the Transducer (2). Refer to Illustration 16.

  29. Operate the vacuum transducer before installing the final drive plugs and the differential case drain plug.

    Note: Be sure that the rear axle oil system has pulled a vacuum. Hot oil could cause personal injury if a vacuum is not pulled.

  30. Remove both final drive adapters (5) and the differential adapter (8). Quickly install all plugs.

    Illustration 17g01285450
    (1) Air breather

  31. Remove the vacuum transducer (2) and reinstall the air breather (1). Refer to Illustration 17.

  32. Check and maintain the oil level in the differential and final drives to the recommended oil level for each truck model according to the Operation and Maintenance Manual.

  33. Reinstall the protective caps to the filter cart hoses to control contamination.

Oil Compartment Times for 188-3242 Filter Cart and 246-1157 Filter Cart

If an on-line portable particle counter is not available to diagnose and track when the contaminant level has lowered to an acceptable level, refer to the following equation. This equation relates to the 188-3242 Filter Cart and the 246-1157 Filter Carts only. Other filtration units will use different equation references. The units which use different equations will be noted when appropriate.

Illustration 18g01177339
Oil compartment filtration equation
(A) Compartment oil capacity (gal)
(B) Pulses per minute
(C) Approximate filtration time (min)

Pulses Per Minute Definition:

Each air discharge or each stroke of the air operated filter pump delivers one pulse of oil. The internal pump shaft will slide left (one pulse), and then to the right (one pulse). This action delivers oil in both directions. Another way of determining pulses is to listen for the (tuk-chuk) of two pulses. Count the number of pulses in 1 minute for use in the above equation.


A 777D Off-Highway Truck rear axle has 227 L (60 US gal) of SAE 60W oil. The filter cart is operating at 80 pulses per minute. The approximate filtration time should be 105 minutes or 1.8 hours.

ISO 4406:1999 Method for Coding the Level of Contamination by Solid Particles

ISO (International Organization of Standardization) is a worldwide federation of national standards bodies. The ISO 4406:1999 specifies the code to be used in defining the quantity of solid particles in the fluid used in any given hydraulic fluid power system. An automatic particle counter derives the equivalent size of a particle from the particles cross sectional area. Particle counts are affected by various factors. These factors include procurement of the sample, the sample container and particle counting accuracy and cleanliness. Proper care should be taken during sample procurement to ensure that the sample obtained is representative of the fluid circulation in the system.

The code for contamination levels using automatic particle counters is comprised of three scale numbers, for example X/Y/Z.

"X" - The number of particles that is equal to or larger than 4 microns.

"Y" - The number of particles that is equal to or larger than 6 microns.

"Z" - The number of particles that is equal to or larger than 14 microns

At this time, Caterpillar does not require the reporting of the "X" scale number since the hydraulic tolerances exceed the 4 micron value. Therefore, a "-" is used instead. For example, a particle count is read as -/Y/Z, meaning that there was no requirement to count particles equal to or larger than 4 microns.

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