T.V. Valve, Plunger & T.V. Modulator Valves

The throttle valve directs oil pressure to the shift valves, increasing pressure in direct proportion to throttle opening. The throttle valve uses a spring and plunger to regulate the amount of pressure applied to the shift valves. At idle, when the plunger is not depressed, pressure applied from the limit valve pushes the throttle valve to the right and pressure applied to the shift valves is nearly zero. As the throttle is opened, the plunger compresses the spring which acts on the throttle valve and the T.V. pressure applied to the shift valves increases until it equalizes with the applied spring pressure. In the shift valves, governor pressure must overcome the T.V. pressure before the shift valve will shuttle and allow the transmission to shift to the next range.

However, as the same T.V. pressure is not ideal for every shift range, modulators are used between the throttle valve and the 3-4 and 4-3 shift valves. These modulators (3-4 M.T.V. and 4-3 M.T.V.) modulate pressure applied to the 3-4 and 4-3 shift valves when throttle valve pressure is at low to medium levels but allow full T.V. pressure to be applied during higher pressure (full throttle) operation.