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Hot hydraulic oil under high pressure can remain in the components of the hydraulic system or the power train system after the engine has been stopped. The uncontrolled release of the hydraulic oil can cause sudden machine movement and can also result in the following conditions:
If hydraulic oil penetrates body tissue, the injury must be treated immediately by a doctor who is familiar with this type of injury. Use a board or a piece of cardboard to check for a hydraulic oil leak. Make sure that all of the attachments have been lowered to the ground and that all trapped pressure has been released from the hydraulic system and the power train system. Also, make sure that the hydraulic oil is cool before the removal of any components or lines. Remove the hydraulic oil filler cap only when the engine is stopped and the filler cap is cool enough to touch with your bare hand. |
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Personal injury or death can result from not engaging the parking brake. Transmission engagement alone will not prevent machine from rolling when the engine is stopped. |
| 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 product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, PERJ1017, "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. |
| Transmission Relief Valve | ||
| Date | Equipment ID Code | |
| Item | Specification | Actual |
| Relief pressure at pressure tap (P) at high idle | |
|
| Relief pressure at pressure tap (P) at low idle | |
|
| |
| Illustration 1 | g02987996 |
| Torque Specifications | |
|---|---|
| Callout | Torque |
| Locknut (2) | |
The main relief valve for the transmission maintains the maximum pressure of the oil delivered to the clutches by the modulating valves. Also, the main relief valve protects the transmission hydraulic system from any high-pressure spikes. The following test procedure will verify whether the pressure setting is within the specified limit. The adjustment procedure provides the information that is needed to adjust the main relief valve to the specified limit.
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| Illustration 2 | g02571852 |
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Tooling (A) | |
| Required Tools | ||||
|---|---|---|---|---|
| Tool | Item | Qty | Part No | Description |
| A | 198-4240 | Digital Pressure Indicator Gp | ||
| A1 | 1 | 198-4234 | Digital Indicator | |
| A2 | 1 | 198-4238(1) | Pressure Sensor Gp
(0 to 34,450 kPa (0 to 5,000 psi)) |
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| A3 | 1 | 198-4236 | Adapter Cable As | |
| (1) | This sensor must be purchased separately, and is not included in the 198-4240 Digital Pressure Indicator Gp |
Test Preparation - Transmission Relief Valve
- Move the machine to a smooth horizontal location.
- Permit only one operator on the machine. Keep all other personnel away from the machine or in the sight of the operator.
- Place the steering control lever in the NEUTRAL position.
- Engage the parking brake.
- Lower the attachments to the ground.
- Stop the engine.
- Turn the key to the ON position, but do not start the engine.
- Verify that the implement shutoff control is in the UNLOCKED position.
- Move the control levers through the full range of travel several times. This action should relieve any pressure that may be present in the implement hydraulic system.
- Loosen the filler cap on the hydraulic tank so that the pressure in the tank is released. The machine may be equipped with a breaker valve. The breaker valve will be on top of the tank. To release the pressure of the tank, press the button on top of the breaker valve (if equipped).
- Tighten the filler cap on the hydraulic tank.
- Make sure that the pressure in the entire hydraulic system has been released.
- Turn the key to the OFF position.
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Illustration 3 g03715470 View of the rear cover of the transmission - Install Tooling (A) onto pressure tap (P).
Reference: Refer to Troubleshooting for additional guidance for preparing the machine for testing.
Note: The monitoring system (if equipped) for your machine accesses many values that are useful in troubleshooting the power train system. When the situation is appropriate, use the monitoring system to find a pressure or determine a system problem.
Test Procedure - Transmission Relief Valve
- Perform steps in the "Test Preparation - Transmission Relief Valve" section.
- Start engine and warm the transmission oil to operating temperature.
- Run the engine at HIGH IDLE. Note the pressure on the gauge. The pressure should be
2650 ± 150 kPa (384 ± 22 psi) . - Run the engine at LOW IDLE. Note the pressure on the gauge. The pressure should be
2525 ± 125 kPa (366 ± 18 psi) - If the pressure that is observed is not within the specified limits, perform the steps in "Adjustment Procedure - Transmission Relief Valve".
Adjustment Procedure - Transmission Relief Valve
- Shut off the engine.
- Remove cover (1) from Illustration 3.
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Illustration 4 g02988037 Note: The main relief valve is located behind cover (1) on the transmission hydraulic control.
- Loosen locknut (2).
- Turn adjustment screw (3) clockwise to increase the pressure setting. Turn adjustment screw (3) counterclockwise to decrease the pressure setting.
Note: One full turn changes the pressure by approximately
120 kPa (17 psi) .Note: Turn adjustment screw (3) counterclockwise past the desired pressure setting. Then, turn adjustment screw (3) clockwise to the correct pressure setting. This method of adjustment eliminates any movement in the threads.
- Tighten locknut (2) to a torque of
18 ± 4 N·m (159 ± 35 lb in) . - Perform the steps in "Test Procedure - Transmission Relief Valve" to verify the pressure adjustments.
