Low oil pressure in the gearbox of a loader forklift can lead to poor performance and potential damage to the transmission system. It is important to identify the underlying reasons and implement appropriate troubleshooting methods. Here are the main causes and troubleshooting steps for low oil pressure in all gears of the loader forklift gearbox:

1. Insufficient Oil Volume in the Gearbox Oil Pan: Check the oil level in the gearbox and ensure it is filled to the specified level. Add hydraulic transmission oil as needed to maintain the proper oil volume.

2. Clogged Transmission Oil Filter: Inspect the transmission oil filter for clogs or blockages. If it is dirty or clogged, clean or replace the oil filter to restore proper oil flow.

3. Poorly Sealed Oil Suction Pipeline: Check the oil suction pipeline running from the transmission oil pan to the variable speed pump. Ensure it is properly sealed without any leaks. Repair or replace the pipeline if necessary to maintain a secure seal.

4. Worn Variable Speed Pump: If the variable speed pump is significantly worn, it can cause internal leakage and result in low oil pressure. In such cases, the variable speed pump should be replaced to restore proper functionality.

5. Improperly Adjusted Pressure Regulating Valve or Damaged Pressure Regulating Spring: Inspect the pressure regulating valve of the variable speed control valve. Check if the pressure regulating spring is damaged or if the valve is improperly adjusted. Replace the spring if necessary and readjust the pressure to the specified value.

6. Stuck Pressure Regulating Valve Stem or Accumulator Piston: If the pressure regulating valve stem or accumulator piston is stuck in the valve body, it can impede proper oil flow and result in low pressure. Disassemble the pressure regulating valve and accumulator for cleaning to resolve any blockages or sticking issues.

It is important to note that oil deterioration can also contribute to low oil pressure. Regularly check the quality of the oil and replace it as needed to maintain optimal performance. Additionally, ensure that the pressure gauge is accurate and functioning properly. If the gauge is faulty or the sensor is damaged, replace or repair them promptly to avoid any false indications of low pressure.

By addressing these potential causes and performing the necessary troubleshooting steps, you can effectively resolve low oil pressure issues in the gearbox of your loader forklift, ensuring smooth and efficient operation. Regular maintenance and monitoring of the gearbox oil level and quality are essential for preventing future problems and extending the lifespan of the transmission system.