TORQUE CONVERTER AND

TRANSMISSION HYDRAULIC SYSTEM

The torque converter housing is the oil sump for the torque converter and transmission oil supply. A four-section torque converter and transmission pump is located at the rear of the torque converter.

The four sections (from rear to front) are:

1. Transmission lube

2. Transmission charging

3. Torque converter charging

4. Transmission scavenge

The transmission lube pump section pulls oil from the end of the manifold that is supplied by the cooler return line. All of the oil going to this section of the pump comes from the cooler return line. Oil flows from the transmission lube section of the pump to the transfer gears. Transmission lube oil flows through the transfer gears and the transmission to cool and lubricate the internal components.

The transmission charging pump section pulls oil from the end of the manifold that is supplied from the sump in the converter housing. All of the oil to this pump section comes from the sump.

A small amount of oil from the transmission charging pump section flows through a priming bleed orifice to the outlet of the lube pump section. Most of the oil flows through the transmission charging filter.

From the filter, transmission charging oil flows in the following

two directions:

1. Transmission charging oil flows to the torque converter lockup clutch valve located on top of the torque converter.

2. Transmission charging oil also flows to the transmission control valves located on top of the transmission. Oil that is not used to actuate the clutches flows back to the converter housing and joins with

flow from the converter charging pump section at the inlet relief valve.

The torque converter charging pump section pulls oil from the middle of the manifold in the torque converter housing. Oil is supplied both from the cooler return line and from the sump. Oil flows from the torque converter charging pump section through the torque converter

charging filter to the torque converter inlet relief valve. Transmission charging oil joins with the torque converter charging oil at the inlet relief valve. The charging oil flows through the torque converter, the outlet relief valve, the

torque converter outlet screen, and the power train oil coolers. The oil flows through the coolers and returns to the torque converter housing.

Final drive

Planetary final drive has full floating axle shafts and a plug in differential carrier assembly

Lubrication System

The engine oil pump draws oil from the oil pan through a screen. The engine also has a scavenge pump at the rear of the engine to transfer oil from the rear of the oil pan to the main sump. Oil flows from the pump through an engine oil cooler bypass valve to the engine oil cooler. The bypass valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. Oil flows from the engine oil cooler to the oil filters. The

oil flows through the filters and enters the engine cylinder block to clean, cool, and lubricate the internal components and the turbochargers. Some trucks are equipped with an engine oil renewal system. Engine oil flows from the engine block to an engine oil renewal system manifold. A small amount of oil flows from the engine

oil renewal system manifold into the return side of the fuel pressure regulator. The engine oil returns to the fuel tank with the return fuel.