PLATE 7N2851 - Caterpillar

Pressure In The Transmission Hydraulic Control System
A number of important components of the power train are supplied and controlled by oil from the transmission pump. The pressure in the system is regulated by the transmission hydraulic control relief valve. This valve serves the dual purpose of regulating the system pressure and supplying the correct pressure of oil to the torque converter.Tests may be carried out in order to determine whether the transmission pump is supplying the correct amount of oil for each of the components in the system.The following pressures can be tested in order to determine whether the oil that is supplied is sufficient.
Transmission Oil Filter Bypass
Transmission Hydraulic Control Valve
Torque Converter Lockup Clutch
Planetary Transmission Clutches
Torque Converter Inlet Pressure
Torque Converter Outlet Pressure
Transmission LubricationTransmission Pump
If insufficient oil pressure is measured anywhere in the transmission hydraulic control system, test the pressure of the oil at the oil filter bypass valve. Refer to Specifications, Systems Operation/Testing and Adjusting, "Hydraulic Oil Contamination - Test". If the pressure at the oil filter bypass valve is within specifications, test the pressure at the transmission hydraulic control relief valve. Refer to Specifications, Systems Operation/Testing and Adjusting, "Relief Valve (Transmission Hydraulic Control) - Test and Adjust".If the pressure at the transmission hydraulic control relief valve is below the specification, the oil filter may be blocked. Remove the oil filter bypass valve and inspect the oil filter bypass valve for wear or damage. If the pressure of the oil at the oil filter bypass valve and the main relief valve is below the specification, the transmission oil pump is damaged or broken. The transmission oil pump is not serviceable and the transmission oil pump must be replaced.