Bench Test Procedure for a 785G Off-Highway Truck Transmission {3030, 3073} Caterpillar

Off-Highway Truck/Tractor

785G (S/N: RTL1-UP)

Introduction

© 2017 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 special instruction contains the necessary information that is required to bench test a specific transmission arrangement. Refer to Table 2 for the correct arrangements. Bench testing the transmission ensures correct assembly and operation of the component. Rotating a transmission provides the most conclusive evaluation. Testing allows the dealer to ensure that the transmission will operate properly in the machine. The specifications in this guideline are specific to bench testing the component. Every effort has been made to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This guideline must be used with the latest technical information that is available from Caterpillar.

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.

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.

Important Safety Information

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Follow all safety warnings. Most accidents that involve product operation, maintenance, or repair are caused by failure to observe safety warnings. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. Personnel must be properly trained to perform maintenance, repair, or operate any machine. Safety precautions and warnings are provided this instruction and on Caterpillar products. These warnings should be observed before performing any procedures. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are not all inclusive.

The hazards are identified by the “Safety Alert Symbol” which is followed by a “Signal Word” such as “DANGER”, “WARNING, or” “CAUTION”. The “WARNING” Safety Alert Symbol is shown in illustration below.

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This safety alert symbol means:

Pay Attention!

Become Alert!

Your Safety is Involved.

The message that appears under the safety alert symbol explains the hazard.

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. The safety information in this document and the safety information on the machine are not all inclusive. Determine that the tools, procedures, work methods, and operating techniques are safe. Determine that the operation, lubrication, maintenance, and repair procedures will not damage the machine. Also, determine that the operation, lubrication, maintenance, and repair procedures will not make the machine unsafe.

The information, the specifications, and the illustrations that exist in this guideline are based on information which was available at the time of publication. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete, most current information before you start any job. Caterpillar dealers can supply the most current information.

Collecting the Test Data

Since conditions vary for each test bench, use the data that is collected from your test bench. The collected data is used to compare test results. The data should be collected and maintained by the operator.

Data from each transmission arrangement is collected and stored. Averages from each transmission arrangement are often used to compare values on portions of transmission tests. Always compare data that is collected from the same transmission arrangement that is being tested. Averages for the last 20 transmission arrangements should be maintained.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

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

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Personal injury or death can result from not following the proper procedures. To avoid the possibility of injury or death, follow the established procedure.

Tools Needed

Note: Pressures will be sensitive to tooling setup. The diameter of the hose, the diameter of a fitting, and extra filtering can affect pressure. The required tools that are listed in Table 3 were used to develop this test procedure.

Installation Procedure

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1. Install Tooling (A) to the test stand.
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2. Use a hoist to install transmission onto Tooling (A). The weight of the transmission is approximately 2268 kg (5000 lb).
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3. Install Tooling (B) to prevent movement of the transmission during test.

   Note: Over-tightening Tooling (B) can jeopardize the tightening ability of the castle nuts on Tooling (A) later in this section.

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4. Install Tooling (C) to the input end of the transmission.
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5. Install Tooling (D) to Tooling (C).

6. Align the transmission with the input drive shaft.
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7. Connect the input drive shaft to Tooling (D).
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8. Close and latch drive shaft guard.
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9. Tighten all four castle nuts and jack bolts.

10. Re-tighten Tooling (B).
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11. Remove Plate (1).
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12. Install Tooling (F) to the output end of the transmission.
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13. Install Tooling (G) onto Tooling (F).
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    Controls (in)

14. Install Tooling (H) to the transmission.
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    Controls (out)

15. Install Tooling (J) to the transmission.
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    Lube (in)

16. Install Tooling (K) to the transmission.
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    Controls (in)

17. Connect Hose Assembly (2) from the pressurized Flowmeter to Tooling (H).
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    Controls (out)

18. Connect Hose Assembly (3) from Tooling (J) to Flowmeter 1 (in).
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    Lube (in)

19. Connect Hose Assembly (4) from Flowmeter 1 (out) to Tooling (K).
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    Lube Pressure

20. Connect a Pressure Gauge to Pressure Tap (5).
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    (6) Controls (out) Pressure (7) Main Relief Pressure (8) Clutch 4 Pressure (9) Clutch 5 Pressure (10) Clutch 6 Pressure (11) Clutch 2 Pressure (12) Clutch 3 Pressure (13) Clutch 1 Pressure

21. Connect Pressure Gauges to Pressure Taps (6-13).
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    Spindle Lube

22. Connect Hose Assembly (14) to Tooling (G).
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23. Install Tooling (L) to the transmission.
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24. Connect Tooling (L) to a suitable location.
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25. Connect Tooling (L) to Tooling (M). Refer to Tool Operating Manual , NEHS0996 for the correct operating instructions.

Test Procedure

TA3 Navigation

1. Select "Off-Highway Truck".

2. Select "785G".

Harness Test

1. Make sure Tooling (L) is properly connected.

2. Use Tooling (M) to perform the harness test.

3. Record the values in Table 6.

   Note: Do not continue testing until Harness Test passes.

Start Check

Note: Due to high torque during the shifting of this transmission, reduce input speed to 400 rpm before shifting into any gear. Re-tighten chains and binders after first shift and monitor during the test.

1. If you are using SAE 10W oil, warm the oil to 50 °C (125 °F). If you are using Mobil DTE11 oil, warm the oil to 34 °C (95 °F). Maintain this temperature during the test.

2. Set the input flow to 151 ± 4 L/min (40 ± 1 US gpm).
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3. With the transmission in the NEUTRAL position, rotate the input shaft in a counterclockwise direction. Adjust the input rotation to 700 ± 20 rpm.

4. The lube pressure should be minimum 14 kPa (2 psi).

   Note: If there is no lube pressure after 30 seconds, stop the test and verify test stand and transmission connections.

5. Shift the transmission through all gears to eliminate air from the transmission controls.

6. Confirm the correct clutch engagement with Table 4.
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   Table 4

   Clutch Engagement Check
   Gear	CL 1	CL 2	CL 3	CL 4	CL 5	CL 6
   N			X
   R	X					X
   F1	X				X
   F2		X			X
   F3	X			X
   F4		X		X
   F5	X		X
   F6		X	X

Low Idle Check

Note: Due to high torque during the shifting of this transmission, reduce input speed to 400 rpm before shifting into any gear. Re-tighten chains and binders after first shift and monitor during the test.

1. With the transmission in neutral position, set input flow to 151 ± 4 L/min (40 ± 1 US gpm).

2. Adjust input rotation to 700 ± 20 rpm.

3. Record Clutch Pressures, Lube Pressure, Main Relief Pressure, Controls (out) Pressure, Lube Flow, and Horse Power Loss in Table 8.

4. Confirm values with Table 7.

5. Reduce input rotation to 400 ± 20 rpm.

6. Shift the transmission to Forward 1.

7. Repeat Steps 2 and 5 for each gear.

   Note: Always shift the transmission back to NEUTRAL when shifting between FORWARD and REVERSE.

High Idle Check

Note: Due to high torque during the shifting of this transmission, reduce input speed to 400 rpm before shifting into any gear. Re-tighten chains and binders after first shift and monitor during the test.

1. With the transmission in neutral position, set the input flow to 151 ± 4 L/min (40 ± 1 US gpm).

2. Adjust input rotation to 1750 ± 20 rpm.

3. Record Clutch Pressures, Lube Pressure, Main Relief Pressure, Controls (out) Pressure, and Lube Flow in Table 10.

4. Confirm values with Table 9.

5. Adjust input rotation to 400 ± 20 rpm.

6. Shift the transmission to Forward 1.

7. Repeat Steps 2 through 5 for each gear.

   Note: Always shift the transmission back to NEUTRAL when shifting between FORWARD and REVERSE.

Speed Sensor Check

Note: Due to high torque during the shifting of this transmission, reduce input speed to 400 rpm before shifting into any gear. Re-tighten chains and binders after first shift and monitor during the test.

1. With the transmission in neutral position, set input flow to 151 ± 4 L/min (40 ± 1 US gpm).

2. Adjust input rotation to 400 ± 20 rpm.

3. Shift the transmission to Forward 1.

4. Adjust input rotation to 700 ± 20 rpm.

5. Record Output Speed 1, Output Speed 2, and Intermediate Speed in Table 12.

6. Confirm values with Table 11.

7. Adjust input rotation to 400 ± 20 rpm.

8. Repeat Steps 4 and 7 for each forward position.

Contamination Control

1. Take an oil sample of the test bench oil supply. Oil contamination must be maximum ISO 16/13.

2. Record the results in Table 13.

3. Remove the transmission from the test bench if the test bench oil supply is within specifications.

Transmission Bench Test Data Sheet

Harness Test

Low Idle Check

High Idle Check

Speed Sensor Check

Contamination Control