If the throttle or modulator valve sticks in the closed throttle position, what symptom is most likely?

If the throttle or modulator valve sticks in the closed throttle position, what symptom is most likely?

• A. No upshifts
• B. Soft early upshifts
• C. Delayed upshifts
• D. No complaint

Answer: (B)

When the throttle or modulator valve sticks in the closed position, the transmission experiences a light-load, high-vacuum condition. In vacuum-modulated automatics, this signals the shift controls to operate with less hydraulic pressure and to shift sooner. The result is a soft, early upshift—the gears change earlier than normal but without a harsh feel. If the valve were stuck open, you’d expect different symptoms (harder or later shifts due to lower vacuum). A complete lack of shifts or no response isn’t consistent with a stuck-closed condition.

When the throttle or modulator valve sticks in the closed position, the transmission experiences a light-load, high-vacuum condition. In vacuum-modulated automatics, this signals the shift controls to operate with less hydraulic pressure and to shift sooner. The result is a soft, early upshift—the gears change earlier than normal but without a harsh feel. If the valve were stuck open, you’d expect different symptoms (harder or later shifts due to lower vacuum). A complete lack of shifts or no response isn’t consistent with a stuck-closed condition.