- Off-Highway Truck:
- 789 (S/N: 9ZC1-UP)
- 789B (S/N: 7EK1-UP)
- 789C (S/N: 2BW1-UP)
Reference: Systems Operation/Testing and Adjusting, SENR1532, "789C Off-Highway Truck Hydraulic System", "Relief Valve-Test and Adjust"
Reference: Operation and Maintenance Manual, SEBU7174, "789C Off-Highway Truck Maintenance", "Hoist, Torque Converter, and Brake Tank-Change"
Reference: Operation and Maintenance Manual, SEBU7174, "789C Off-Highway Truck Maintenance", "Lubricant Viscosities and Refill Capacities"
Description of Change: New cast iron pumps are available for the 789C Off-Highway Truck. The new cast iron pumps will allow the pressure of the hoist system to be increased. This will improve dumping performance on adverse grades. Increased pressure and changes in the flow rate of the two pump groups cause the dump time to increase by approximately 1.5 seconds.
Adaptable To: The 175-6253 Gear Pump and the 8E-3882 Gear Pump are effective with 789C (S/N: 2BW129) Off-Highway Truck. The 175-6253 Gear Pump and the 8E-3882 Gear Pump are adaptable to the following trucks: 789 (S/N: 9ZC) Off-Highway Trucks, 789B (S/N: 7EK) Off-Highway Trucks and 789C (S/N: 2BW) Off-Highway Trucks. Use the following procedure to install the new pumps.
Note: The 175-6253 Gear Pump and the 8E-3882 Gear Pump must be used together. Do not replace one pump without replacing the other pump.
| Parts for Removal | |||
|---|---|---|---|
| Item | Quantity | Part Number | Description |
| 1 | 1 | 4T-2606 | Gear Pump |
| 2 | 8 | 8T-9389 | Bolt |
| 3 | 2 | 8W-5179 | Adapter |
| 4 | 2 | 4J-0524 | O-Ring Seal |
| 5 | 1 | 6T-6146 | Gear Pump |
| 6 | 1 | 8W-9963 | Hose As |
| 7 | 1 | 162-2992 | Hose As |
Removal Procedure
- Drain the hydraulic oil from the hydraulic tank into a suitable container. The capacity of the hydraulic tank is 420 L (111 US gal). Refer to Operation and Maintenance Manual, "Hoist, Torque Converter, and Brake Tank - Change" for the correct procedure.
| NOTICE |
|---|
Keep all parts clean from contaminants. Contamination of the hydraulic system with foreign material will reduce the service life of the hydraulic system components. To prevent contaminants from entering the hydraulic system, always plug or cap the lines, fittings, or hoses as they are disconnected. Cover any disassembled components and clean them properly before assembly. Clean the hydraulic system properly after any major component exchange or especially after a component failure, to remove any contamination. |
| NOTICE |
|---|
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. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide", for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose of all fluids according to local regulations and mandates. |
Note: Install caps and plugs on all openings in order to prevent dirt or debris from entering the system. Cleanliness is an important factor. Before the removal procedure, the exterior of the component should be thoroughly cleaned. This will help to prevent dirt from entering the internal mechanism.
Note: For easier assembly, mark all components and hardware for identification purposes.
- Position a suitable container under 4T-2606 Gear Pump (1) in order to contain the hydraulic oil for storage or disposal.
 | |
| Illustration 1 | g00750568 |
- Disconnect four hose assemblies (A) from 4T-2606 Gear Pump (1). Retain the hoses and the associated attached parts. Discard eight 8T-9389 Bolts (2), two 8W-5179 Adapters (3) (not shown), and 4J-0524 O-Ring Seals (4) (not shown).
 | |
| Illustration 2 | g00750578 |
Note: Label four hose assemblies (A) on 4T-2606 Gear Pump (1) with the proper identification.
- Position a suitable lifting sling around 4T-2606 Gear Pump (1). Secure the lifting sling to a hoist.
Note: The weight of 4T-2606 Gear Pump (1) is 57 kg (126 lb).
- Remove nuts (B) and washers (C) that hold 4T-2606 Gear Pump (1) to the pump drive. Retain nuts (B) and washers (C). Remove 4T-2606 Gear Pump (1).
 | |
| Illustration 3 | g00750584 |
- Remove 8W-9963 Hose As (6) and 162-2992 Hose As (7) from 6T-6146 Gear Pump (5). Retain the hardware.
 | |
| Illustration 4 | g00944999 |
Note: 6T-6146 Gear Pump (5) is mounted on the rear of the 6T-6149 Gear Pump .
Note: Label the appropriate hose connections "SUCTION" and "DISCHARGE".
- Position a suitable lifting sling around 6T-6146 Gear Pump (5). Secure the lifting sling to a hoist.
Note: The weight of 6T-6146 Gear Pump (5) is 53 kg (117 lb).
- Remove the bolts and washers that hold 6T-6146 Gear Pump (5). Retain the bolts and washers. Remove 6T-6146 Gear Pump (5) .
Installation Procedure
| Parts for Installation | |||
| Item | Quantity | New Part Number | Description |
| 8 | 1 | 175-6253 | Gear Pump |
| 9 | 8 | 5P-2566 | Bolt |
| 10 | 1 | 8E-3882 | Gear Pump |
| 11 | 1 | 166-9436 | Hose As |
| 12 | 1 | 166-9373 | Hose As |
- Position the lifting sling around 175-6253 Gear Pump (8). Secure the lifting sling to the hoist. Position 175-6253 Gear Pump (8) for installation.
 | |
| Illustration 5 | g00945000 |
Note: 175-6253 Gear Pump (8) directly replaces 4T-2606 Gear Pump (1). 175-6253 Gear Pump (8) has pressure taps with quick disconnects that are installed on the discharge ports. The pressure taps with quick disconnects replace 8W-5179 Adapter and the fittings that are in the pressure tap.
- Attach 175-6253 Gear Pump (8) to the pump drive with existing bolts (B) and existing washers (C) .
- Use eight 5P-2566 Bolts (9) (not shown) to attach the hoses to the top of the pump. Use the existing hardware to attach the lower hoses to the pump.
- Position the lifting sling around 8E-3882 Gear Pump (10). Secure the lifting sling to the hoist. Position 8E-3882 Gear Pump (10) for installation.
 | |
| Illustration 6 | g00945002 |
- Attach 8E-3882 Gear Pump (10) with the existing bolts and the existing washers.
- Use the existing hardware to install 166-9436 Hose Assembly (11) and 166-9373 Hose As (12) .
 | |
| Illustration 7 | g00945003 |
Note: 166-9436 Hose Assembly (11) directly replaces the suction hose. 166-9373 Hose As (12) directly replace the discharge hose.
- To increase the pressure, refer to the procedure for the appropriate truck.
Procedure to Increase the Pressure of the Hoist System of 789 Off-Highway Trucks, of 789B Off-Highway Trucks, and of 789C (S/N: 2BW1-128) Off-Highway Trucks
- Complete Step 1 through Step 6 of the Installation Procedure.
- Add shims to the hoist relief valve that is located in the tank.
- Adjust the relief valve settings to 18961 ± 345 kPa (2750 ± 50 psi).
- Fill the hydraulic tank with hydraulic oil. Refer to Operation and Maintenance Manual, "Hoist, Torque Converter, and Brake Tank-Change" for the correct procedure. Refer to Operation and Maintenance Manual, "Lubricant Viscosities and Refill Capacities" for the correct refill capacity.
Procedure to Increase the Pressure of the Hoist System of 789C (S/N: 2BW129-UP) Off-Highway Trucks
- Complete Step 1 through Step 6 of the Installation Procedure.
- Fill the hydraulic tank with hydraulic oil. Refer to Operation and Maintenance Manual, "Hoist, Torque Converter, and Brake Tank-Change" for the correct procedure. Refer to Operation and Maintenance Manual, "Lubricant Viscosities and Refill Capacities" for the correct refill capacity.
- Increase 132-2048 Control Valve adjustment that is located on the hoist diverter valve. The hoist diverter valve is mounted on the inside frame rail on the rear right hand side of the truck. Refer to Systems Operation/Testing and Adjusting, "Relief Valve-Testing and Adjusting" for the correct procedure.
Note: If the machine is equipped with 164-9234 Control Valve, then no adjustment should be necessary.
- Adjust the relief valve settings to 18961 ± 345 kPa (2750 ± 50 psi).