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Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic systems. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component. Lower all attachments to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the attachment in the raised position, the attachments and lift cylinders must be supported properly. Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made. |
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| NOTICE |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the machine. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Dispose of all fluids according to local regulations and mandates. |
Introduction
The torque converter inlet relief valve limits the maximum pressure from the transmission to the torque converter. The following test should be performed with cold oil.
The following test will check the maximum pressure of the power train oil that is delivered from the transmission to the torque converter. The pressure setting on the torque converter inlet relief valve is not adjustable.
| NOTICE |
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Inlet pressure to the torque converter must not be over 930 ± 35 kPa (135 ± 5 psi). Higher pressures will damage the torque converter. Adjustment of the inlet relief valve must only be done during a bench test and with oil at operating temperature. |
Required Tooling
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| Illustration 1 | g02689390 |
Digital Pressure Indicator Group (A) | |
| Tool | Item | Qty | Part No | Description |
|---|---|---|---|---|
| A | 198-4240 | Digital Pressure Indicator Gp | ||
| A1 | 1 | 198-4234 | Digital Indicator | |
| A2 | 1 | 198-4237 | Pressure Sensor Gp (0 to 3,445 kPa (0 to 500 psi)) |
|
| A3 | 1 | 198-4236 | Adapter Cable As | |
Machine Preparation
- Move the machine to a smooth horizontal location. Move away from any machines that are working and any personnel.
- Move the transmission control to the NEUTRAL position. Fully raise the dump body of the truck.
- Activate the parking brakes. Stop the engine.
- Permit only one operator on the machine. Either keep other personnel away from the machine, or keep other personnel in the sight of the operator.
- Place blocks in front of the wheels and behind the wheels.
- Install the retaining pin for the dump body.
- Make sure that the transmission is in the NEUTRAL position.
- Make sure that all air pressure and oil pressure is released before any fittings, hoses, or components are worked on.
- Push the brake pedal many times until there is no brake pressure.
Test Procedure
Note: Only perform this test when the torque converter oil (SAE 30 W) is below 30° C (86° F).
Note: Make sure that the filters and the screens are clean before you test any pressures.
- Connect Tooling (A) to the nipple at pressure tap (1) .
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| Illustration 2 | g02635060 |
View of the right side of the transmission (1) Pressure tap for the torque converter inlet | |
- Start the engine while the parking brakes are engaged. Run the engine at the low idle rpm while the transmission is in NEUTRAL. The pressure on the gauge must be a minimum of 4 kPa (0.5 psi).
- Run the engine at the high idle rpm while the transmission is in NEUTRAL. The pressure on the gauge must be 930 ± 103 kPa (135 ± 15 psi).
- When this test is complete, stop the engine and remove the test equipment.
Problem
The pressure of the pump section for charging the transmission is correct and the transmission lubrication pressure is too low.
Probable Cause
- The relief valve for the torque converter is open.
- There is too much leakage in the torque converter circuit.
- There is too much leakage in the transmission lubrication circuit.
Problem
The oil gets too hot during normal operation.
Probable Cause
- There is to much oil in the transmission case. Perform the check in the Power Train Testing and Adjusting, "Transmission troubleshooting".
Worksheet
| Pressure | |
| Target | Actual |
930 ± 103 kPa (135 ± 15 psi) |
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