58 Hydraulic gear selection control operation

5.8.1 Fluid flow in neutral (Fig. 5.24) Pressurized oil from the pump flows to the main pressure regulating valve. The valve shifts over due to the oil pressure, thus opening a passage supplying the torque converter via the converter pressure valve. Increased pump pressure moves the valve further until it uncovers the exhaust port dumping the oil back into the oil pump suction intake passage.

The oil pressure generated between the pump and main pressure limiting valve is known as line pressure and is directed to the throttle pressure limiting valve, accumulator, manual selection valve and through the latter valve to the 2-3 shift valve.

When the throttle foot released, the intermediate pressure exhausts so that there will be no throttle pressure. Depressing the throttle pedal increases the throttle spring tension and creates a throttle pressure which is then directed to the kickdown valve, main pressure limiting valve, 1-2 shift valve and the 2-3 shift valve.

At the same time, a limited throttle pressure is created between the main pressure limiting valve and main pressure regulating valve. This pressure is also directed to the soft engagement valve.

With the manual gear selector valve in neutral, there is no line pressure to the rear of the main regulating valve and therefore the trapped line pressure will be at a maximum.

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