3.2 Hydraulic system of torque converter and transmission

The oil in transmission oil pan is sucked by transmission pump and delivered to the pressure reducing valve (see Figure 3-2) via filter (installed with bypass valve, when filter is blocked, oil is discharged from bypass valve. The pressure difference of bypass valve is 0.3Mpa). High-pressure oil is flowed to the upper end of pressure reducing valve from small hole of pressure reducing valve rod (2) (see figure 3-3) and push down the pressure reducing valve rod.

High-pressure oil will flow in two channels, one is for entering the torque converter via torque converter oil inlet pressure valve, the other is for entering the transmission valve via clutch cut-off valve. High-pressure oil can get into different piston cylinder of clutch to obtain different gear when the speed change distributor valve rod (4) is moved manually.

Meanwhile, high-pressure oil enters the slide block (7) under the pressure valve via small hole to move the slide block up to stably control oil pressure to 1.2-1.5Mpa.

After the returned oil of torque converter is cooled in cooler, it enters to transmission via lubrication pressure valve for lubrication and cooling. Pressure of lubrication pressure valve is 0.1-0.2Mpa(1-2kg／cm²).

3.3 Maintenance of torque converter and transmission

Proper running of torque converter and transmission is important to the performance of entire machine. So, besides the regular maintenance, pay more attention to the following:

3.3.1 Transmission oil level

Before starting the engine, check two oil drain plugs at right side of transmission. The upper plug is maximum limit and the lower one is the minimum limit.

3.3.2 Torque converter and transmission oil pressure

The inlet & outlet pressure of torque converter has been preset by manufacturer before shipment. After engine is started, the pressure gauge for transmission oil should reads within 1.2—1.5Mpa.

Figure 3-2 Block Diagram of Oil Channel for Transmission and Torque Converter

1. Cooler	2. Torque converter	3. Torque converter oil inlet pressure valve
4. Filter	5. Transmission pump	6. Pressure reducing valve
7. Clutch cut-off valve	8. Transmission valve	9. Speed I clutch
l0. Speed II clutch	11. Reverse clutch	12. Lubrication pressure valve

3.3.3 Oil temperature

For normal work and running, the highest oil temperature should not exceed 120℃. In case it exceeds, you should stop the vehicle and engine. After the machine is cooled down, make inspection.

3.3.4 After the break-in period, please change the transmission oil periodically (usually every 600 hours). Immediate oil change should be made whenever the oil is spoiled or foreign material is found in oil.

Figure 3-3 Speed control valve

1. Bolt 2. Pressure reducing valve rod

3. Brake valve rod 4. Distributor valve rod

5. Air valve stem 6. Plunger

7. Slide rod