If a modulator valve vacuum line is disconnected, the transmission would upshift at what speeds?

If a modulator valve vacuum line is disconnected, the transmission would upshift at what speeds?

• A. Earlier than normal
• B. At normal speeds
• C. No upshifts
• D. Upshifts would occur at much higher speeds than normal

Answer: (D)

The vacuum modulator uses engine vacuum to control when shifts happen. High vacuum (light load) makes shifts occur earlier, while low or no vacuum (heavy load or a disconnected line) delays shifts to higher engine speeds. If the vacuum line to the modulator is disconnected, the modulator loses its signal and behaves as if the engine is under heavy load, so upshifts occur at much higher speeds than normal.

The vacuum modulator uses engine vacuum to control when shifts happen. High vacuum (light load) makes shifts occur earlier, while low or no vacuum (heavy load or a disconnected line) delays shifts to higher engine speeds. If the vacuum line to the modulator is disconnected, the modulator loses its signal and behaves as if the engine is under heavy load, so upshifts occur at much higher speeds than normal.