ENGINE AR 4W1988 - Caterpillar

Pressure In The Transmission Hydraulic Control System
The oil supply for the transmission can be tested at various points around the transmission hydraulic 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. The following pressures can be tested in order to determine whether the oil that is supplied is sufficient.
Transmission Hydraulic Control Relief Valve
Torque Converter Lockup Clutch
Planetary Transmission Clutches
Relief Pressure For The Torque Converter Inlet Transmission 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 Systems Operation, Testing and Adjusting, "Power Train Pressures". If the pressure at the oil filter bypass valve is within specifications, test the pressure at the transmission hydraulic control relief valve.If the pressure at the transmission hydraulic control relief valve is below the specification, check the oil filter and oil filter bypass valve. The oil filter may be blocked and the oil filter bypass valve is not functioning. 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 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. Oil Supply To The Torque Converter
The oil supply to the torque converter is determined by the torque converter inlet relief valve. The torque converter inlet relief valve is used to supply a constant pressure of oil to the torque converter. The torque converter transmits torque between the engine and the planetary transmission. The torque converter inlet relief valve is located in the same valve body as the transmission hydraulic control relief valve. The torque converter inlet relief valve is nonadjustable.Test the relief pressure for the torque converter inlet. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures". If the pressure is outside the specifications, test the pump supply pressure on the oil filter bypass valve. Refer to Systems Operation, Testing and Adjusting, "Power Train Pressures". If the pump supply pressure is not correct, replace the torque converter inlet relief valve.