574B Forwarder Power Train Caterpillar

The following procedure can be used as a first step to check the performance of the drive loop. If there is excessive internal leakage in a component of the drive loop, the machine may experience a loss of rimpull.

The Forwarder uses a power train pump to provide oil flow to the drive loop. A charge pump is mounted on the power train pump.

The charge pump provides makeup oil flow to the power train pump. Charge pump oil prevents cavitation in the power train pump.

Illustration 1	g00916687
Power Train Pump (1) Oil line (drive loop) (forward). (2) Charge pressure relief valve. (3) Oil line (drive loop) (reverse). (4) Charge pump. (5) Relief valve (cold oil start-up).

The oil pressure in the charge system is controlled by relief valve (2). Relief valve (2) will open when the oil pressure in the charge system exceeds 2300 kPa (334 psi).

Relief valve (5) protects the charge system from cold oil or restrictions in the charge system. Relief valve (5) will open when the oil pressure exceeds 3000 kPa (435 psi).

Table 1

Required Parts
Part	Part Number	Part Description	Qty
A	5P-0047	Covers	2
B	1P-3703	Rectangular Seals	2

1. Tilt the cab.

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Illustration 2	g00916696
(6) Wire connector. (7) Parking brake valve.

2. Disconnect wire (6) from parking brake valve (7) .

   This prevents the parking brake from disengaging.

3. Tilt down the cab.

4. Start the engine.

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Illustration 3	g00916713

5. At the main menu of the IQAN display, press the right arrow key. The following window will appear.

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Illustration 4	g00916714

6. Allow the machine to warm up. Ensure that the hydraulic oil is at normal operating temperature.

7. Read the charge pressure on the IQAN display. The pressure reading should not exceed 23 bar. The charge pressure should not drop below 12 bar.

8. Place the direction selector switch in the FORWARD position. Place the machine in HIGH speed.

9. Slowly depress the accelerator pedal until the accelerator pedal is on the floor. Note the pressure reading on the IQAN display. The pressure reading should not drop below 12 Bar.

   Note: In order to prevent damage to the power train pump, do not hold down the accelerator pedal to the floor for more than 10 seconds.

10. Release the accelerator pedal and stop the engine.

11. Perform Steps 12 and 13 if the charge pressure dropped below 12 Bar.

    If the charge pressure dropped below 12 Bar, there is excessive leakage in the power train pump or the power train motor.

    Steps 12 and 13 will isolate the test to the power train pump.

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Illustration 5	g00916687
Power Train Pump (1) Oil line (drive loop) (forward). (2) Charge pressure relief valve. (3) Oil line (drive loop) (reverse). (4) Charge pump. (5) Relief valve (cold oil start-up).

12. Disconnect oil lines (1) and (3). Use covers (A) and rectangular seals (B) to block ports "P2(S)" and "S(P2)" on the power train pump.

    Note: When high pressure oil flows from the "P2(S)" port, the machine travels forward. When high pressure oil flows from the "S(P2)" port, the machine travels backward.

13. Repeat Step 4 through Step 10.

    If the charge pressure dropped below 12 Bar, there is excessive leakage in the power train pump.

    If the charge pressure was within specifications, perform the procedures in Systems Operation Testing and Adjusting, "Hydrostatic Drive System Performance - Test".