Pressure Regulator
The pressure regulator limits the maximum amount of oil pressure developed by the oil pump. It is a spring-loaded valve that routes excess pump pressure out of the hydraulic system, assuring proper transmission operation.
Figure 4-36.- Typical transmission hydraulic pump.
Manual Valve Vacuum Modulator Valve
A manual valve (fig. 4-37), operated by the shift The vacuum modulator valve (fig. 4-38) is a mechanism, allows the operator to select park, neutral, diaphragm device that uses engine manifold vacuum to reverse, or different drive ranges. A manual valve is indicate engine load to the shift valve. As engine basically a multiport spool valve that switches line vacuum (load) rises and falls, it moves the diaphragm pressure to selected passages, as it is moved through its inside the modulator. This, in turn, moves the rod and operating positions. hydraulic valve to change throttle control pressure in
Figure 4-37.- Manual valve operation.
Figure 4-38.- Vacuum modulator valve.
the transmission. In this way, the vacuum modulator can match transmission shift points to engine loads.
