the transmission. In this way, the vacuum modulator can match transmission shift points to engine loads.
The governor valve (fig. 4-39) senses engine speed (transmission output shaft speed) to help control gear shifting. The vacuum modulator and governor work together to determine shift points. The governor gear is meshed with a gear on the transmission output shaft. Whenever the vehicle and output shaft are moving, the centrifugal weights rotate. When the output shaft and weights are spinning slowly, the weights are held in by the governor springs, causing low-pressure output and the transmission remains in low gear. As the engine speeds increases, the weights are thrown out further and governor pressure increases, moving the shift valve and causing the transmission to shift into higher gear.
Figure 4-39. - Operation of the governor.
Figure 4-40. - Shift valve.Continue Reading